Method, base station, and user equipment for transmitting downlink control signal

ABSTRACT

The application pertains to a method for transmitting a downlink control signal. A base station maps an enhanced physical downlink control channel (E-PDCCH) sequentially to resource elements for transmitting the E-PDCCH in each orthogonal frequency division multiplexing (OFDM) symbol according to an order of OFDM symbols used by the E-PDCCH of a user equipment (UE). The E-PDCCH is sent to the UE from the base station by using the resource elements, where the E-PDCCH and a physical downlink shared channel (PDSCH) invoked by the E-PDCCH are frequency-division multiplexed. Because the E-PDCCH is mapped sequentially to resource elements for transmitting the E-PDCCH in each OFDM symbol according to an order of OFDM symbols used by the E-PDCCH of the UE, different control channel elements of E-PDCCHs at different aggregation levels will not include a same E-PDCCH modulation symbol, thereby ensuring that the UE judges a start position of the E-PDCCH correctly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201210070953.6, filed with the Chinese Patent Office on Mar. 16, 2012,and entitled “METHOD, BASE STATION, AND USER EQUIPMENT FOR TRANSMITTINGDOWNLINK CONTROL SIGNAL”, which is incorporated herein by reference inits entirety.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofcommunications technologies, and in particular, to a method, a basestation, and a user equipment for transmitting a downlink controlsignal.

BACKGROUND

In a 3GPP (3^(rd) Generation Partnership Project) LTE (Long TermEvolution)/LTE-A (LTE-advanced) system, a downlink multiple access modegenerally used is an OFDMA (Orthogonal Frequency Division MultipleAccess) mode. In terms of time, downlink resources of the system aredivided into OFDM (Orthogonal Frequency Division Multiplexing) symbols,and in terms of frequency, the downlink resources of the system aredivided into subcarriers.

In LTE release 8, LTE release 9 and LTE release 10, one downlinksubframe includes two timeslots, and each timeslot includes 7 or 6 OFDMsymbols, so that a downlink subframe includes 14 or 12 OFDM symbols. OnePRB (Physical Resource Block) includes 12 subcarriers in a frequencydomain, and one timeslot in a time domain, which means that one PRBincludes 7 or 6 OFDM symbols. A subcarrier in an OFDM symbol is called aResource Element (RE), and therefore one PRB includes 84 or 72 REs. Inone subframe, two PRBs of two timeslots at a same frequency position arecalled a physical resource block pair; and in LTE, a resourcegranularity of downlink transmission is a physical resource block (PRB)pair.

In LTE release 10 and earlier LTE systems, a physical downlink controlchannel (PDCCH) and a physical downlink shared channel (PDSCH) aretime-division multiplexed in one subframe. The PDCCH is borne on thefirst n symbols of a subframe, and downlink data that the PDCCHschedules is mapped from the (n+1)^(th) symbol of the subframe. In onesubframe, all PDCCHs scheduling user equipments (UEs) are multiplexedtogether, and are then sent in a PDCCH area. One PDCCH may be formed by1, 2, 4 or 8 control channel elements (CCEs); one CCE is formed by 9resource element groups (REGs); and one REG occupies 4 REs.

In LTE release 10 and earlier LTE systems, according to an index of thefirst CCE of a downlink grant (DL_grant) for scheduling a UE, that is, astart position of an enhanced physical downlink control channel E-PDCCH(Enhanced PDCCH), a physical uplink control channel (PUCCH) format 1a/1bchannel may be determined in an implicit manner to bear ACK/NACK(Acknowledgement/Negative-acknowledgement) feedback information fordownlink data transmission.

As control information in a PDCCH is obtained by means of convolutionalencoding with master code being 1/3 and circular buffering based ratematching, when an encoding rate is less than 1/3, it may occur thatdifferent CCEs include a same modulation symbol. For example, when thePDCCH is formed by 4 CCEs, each including 72 bits, the PDCCH can carrytotally 288 encoded bits. Assuming that the PDCCH originally has 48bits, the bit number becomes 144 after the 1/3 encoding, and becomes 288after the circular buffering based rate matching, which is equivalent toa repetition encoding; and the 288 bits are finally mapped to the fourCCEs of the PDCCH. Therefore, modulation symbols in the third CCE andthe fourth CCE are completely the same as modulation symbols in thefirst CCE and the second CCE.

Under the foregoing situation, a base station sends a PDCCH ataggregation level (AL) 4, but when performing blind detection, a UE maypossibly detect information in the third CCE and the fourth CCE as aPDCCH at aggregation level 2. Therefore, the UE may determine a PUCCHformat 1a/1b channel in an implicit manner according to an index of thefirst CCE of the PDCCH at aggregation level 2, that is, an index of thethird CCE. However, the base station may regard that the PUCCH format1a/1b channel allocated to the UE is determined by the first CCE, sothat feedback information cannot be correctly transmitted. It can beseen that unclearness of the CCE detection (that is, incorrect judgmenton the start position of the E-PDCCH) will lead to unclearness of thePUCCH format 1a/1b channel determined by the UE.

In a LTE system later than release 10, with introduction of a multi-usermulti-input multi-output antenna system (MIMO antenna system) andcoordinated multi-point (CoMP) transmission and like technologies, acontrol channel capacity is restricted. Therefore, a PDCCH, which istransmitted based on a MIMO pre-coding mode is introduced and the PDCCHcan be demodulated based on a UE-specific reference signal, that is, ademodulation reference signal (DMRS), and the PDCCH here is also calledan E-PDCCH. An E-PDCCH is not in a control area of the first n symbolsof a subframe, but is in a downlink data transmission area of thesubframe, and is frequency-division multiplexed with a PDSCH, and mayoccupy a different PRB pair from that occupied by the PDSCH, or anE-PDCCH and a PDSCH may be multiplexed in a same PRB pair. In addition,a group of PRB pairs for E-PDCCH(s) may be configured for a cell, sothat each UE in the cell knows all the PRB pairs for E-PDCCH(s) that areconfigured by a base station; or, a PRB pair for E-PDCCH transmissionmay be configured for each UE, which means that PRB pairs for E-PDCCHsthat different UEs need to detect may be different.

Using LTE release 11 as an example, a reference signal of an E-PDCCH isa UE-specific reference signal, and can support 4 ports (that is, DMRSports 7, 8, 9 and 10 for PDSCH demodulation in LTE release 10). A datapart of an E-PDCCH is used to bear modulation symbols of controlinformation after coding and modulation.

An E-PDCCH CCE, hereinafter called an eCCE, is also defined in LTErelease 11. Using a localized E-PDCCH as an example, there are many REsthat can be used to transmit an E-PDCCH in a PRB pair, and these REs mayfurther be divided into several eCCEs. An E-PDCCH is formed by one ormore eCCEs by means of aggregation, and needs to be blindly detected bya UE. As control information in the E-PDCCH is also obtained by means ofconvolutional encoding with master code being 1/3 and circular bufferingbased rate matching, a problem also exists that a UE judges a startposition of the E-PDCCH incorrectly.

SUMMARY

Embodiments of the present invention provide a method, a base station,and a user equipment for transmitting a downlink control signal, that aUE judging a start position of an E-PDCCH incorrectly can be avoided.

According to one aspect, a method for transmitting a downlink controlsignal is provided, including: mapping, by a base station according toan order of OFDM symbols used by a physical downlink control channelE-PDCCH of a user equipment UE, the E-PDCCH sequentially to resourceelements used to transmit the E-PDCCH in each OFDM symbol; and sending,by the base station, the E-PDCCH to the UE by using the resourceelements.

According to another aspect, a method for transmitting a downlinkcontrol signal is provided, including: receiving, by a user equipmentUE, a downlink subframe from a base station; and extracting, by the UEin a blind detection process according to an order of OFDM symbols usedby a candidate E-PDCCH in the downlink subframe, modulation symbols ofthe candidate E-PDCCH sequentially from resource elements used totransmit the candidate E-PDCCH in each OFDM symbol, and performingdecoding and cyclic redundancy check CRC on the candidate E-PDCCH.

According to another aspect, a method for transmitting a downlinkcontrol signal is provided, including: determining, by a base station, areference signal port according to an aggregation level of a physicaldownlink control channel E-PDCCH of a user equipment UE, where E-PDCCHsat different aggregation levels correspond to different reference signalports, and the aggregation level indicates the quantity of controlchannel elements included in the E-PDCCH; and sending, by the basestation, the E-PDCCH to the UE in a subframe, and sending a referencesignal of the E-PDCCH to the UE by using the determined reference signalport.

According to another aspect, a method for transmitting a downlinkcontrol signal is provided, including: receiving, by a user equipment UEfrom a reference signal port in a subframe, a reference signal of acandidate E-PDCCH sent by a base station, where candidate E-PDCCHs atdifferent aggregation levels correspond to different reference signalports, and the aggregation level indicates the quantity of controlchannel elements included in the candidate E-PDCCH; and performing, bythe UE, channel estimation according to the reference signal, so as todemodulate the candidate E-PDCCH.

According to another aspect, a method for transmitting a downlinkcontrol signal is provided, including: sending, by a base station, areference signal of the E-PDCCH by using a first reference signal portv; sending, by the base station, a reference signal of the PDSCH byusing at least one second reference signal port; and determining, by thebase station, not to use a second reference signal port p(v) to send thereference signal of the PDSCH, so that a reference signal port of theE-PDCCH and a reference signal port of the PDSCH are processed based onorthogonal time extensions with different lengths, where the firstreference signal port is one of the at least one second reference signalport, and v and p(v) are serial numbers of the reference signal ports.

According to another aspect, a method for transmitting a signal isprovided, including: receiving, by a user equipment UE, a referencesignal of a physical downlink control channel E-PDCCH which is sent by abase station by using a first reference signal port v and a referencesignal of a physical downlink shared channel PDSCH which is sent by thebase station by using at least one second reference signal port, wherethe PDSCH is invoked by the E-PDCCH; performing, by the UE, channelestimation by using the reference signal of the E-PDCCH, so as todemodulate the E-PDCCH, and performing channel estimation by using thereference signal of the PDSCH, so as to demodulate the PDSCH; anddetermining, by the UE, not to use a reference signal of the PDSCH sentby a second reference signal port p(v) to perform channel estimation, sothat a reference signal port of the E-PDCCH and a reference signal portof the PDSCH are processed based on orthogonal time extensions withdifferent lengths, where the first reference signal port is one of theat least one second reference signal port, and v and p(v) are serialnumbers of the reference signal ports.

According to another aspect, a base station is provided, including: amapping unit, configured to map, according to an order of OFDM symbolsused by a physical downlink control channel E-PDCCH of a user equipmentUE, the E-PDCCH sequentially to resource elements used to transmit theE-PDCCH in each OFDM symbol; and a sending unit, configured to send theE-PDCCH to the UE by using the resource elements.

According to another aspect, a user equipment is provided, including: areceiving unit, configured to receive a downlink subframe from a basestation; and an extracting unit, configured to extract, in a blinddetection process according to an order of OFDM symbols used by acandidate E-PDCCH in the downlink subframe, modulation symbols of thecandidate E-PDCCH sequentially from resource elements used to transmitthe candidate E-PDCCH in each OFDM symbol, and perform decoding and CRCcheck on the candidate E-PDCCH.

According to another aspect, a base station is provided, including: adetermining unit, configured to determine a reference signal portaccording to an aggregation level of a physical downlink control channelE-PDCCH of a user equipment UE, where E-PDCCHs at different aggregationlevels correspond to different reference signal ports, and theaggregation level indicates the quantity of control channel elementsincluded in the E-PDCCH; and a sending unit, configured to send theE-PDCCH to the UE in a subframe, and send a reference signal of theE-PDCCH to the UE by using the determined reference signal port.

According to another aspect, a user equipment is provided, including: asending unit, configured to receive a reference signal of a candidateE-PDCCH from a reference signal port in a subframe, where candidateE-PDCCHs at different aggregation levels correspond to differentreference signal ports, and the aggregation level indicates the quantityof control channel elements included in the candidate E-PDCCH; and ademodulating unit, configured to perform channel estimation according tothe reference signal, so as to demodulate the candidate E-PDCCH.

According to another aspect, a base station is provided, including: asending unit, configured to send a reference signal of the E-PDCCH byusing a first reference signal port v, and send a reference signal ofthe PDSCH by using at least one second reference signal port; and adetermining unit, configured to determine not to use a second referencesignal port p(v) to send the reference signal of the PDSCH, so that areference signal port of the E-PDCCH and a reference signal port of thePDSCH are processed based on orthogonal time extensions with differentlengths, where the first reference signal port is one of the at leastone second reference signal port, and v and p(v) are serial numbers ofthe reference signal ports.

According to another aspect, a user equipment is provided, including: areceiving unit, configured to receive a reference signal of a physicaldownlink control channel E-PDCCH which is sent by a base station byusing a first reference signal port v and a reference signal of aphysical downlink shared channel PDSCH which is sent by the base stationby using at least one second reference signal port, where the PDSCH isinvoked by the E-PDCCH; a demodulating unit, configured to performchannel estimation by using the reference signal of the E-PDCCH, so asto demodulate the E-PDCCH, and perform channel estimation by using thereference signal of the PDSCH, so as to demodulate the PDSCH; and adetermining unit, configured to determine not to use a reference signalof the PDSCH sent by a second reference signal port p(v) to performchannel estimation, so that a reference signal port of the E-PDCCH and areference signal port of the PDSCH are processed based on orthogonaltime extensions with different lengths, where the first reference signalport is one of the at least one second reference signal port, and v andp(v) are serial numbers of the reference signal ports.

In the technical solutions, the E-PDCCH can be mapped, according to anorder of OFDM symbols used by an E-PDCCH of a UE, sequentially toresource elements used to transmit the E-PDCCH in each OFDM symbol, sothat different control channel elements will not include a same E-PDCCHmodulation symbol, thereby avoiding that the UE incorrectly judges astart position of the E-PDCCH.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments or theprior art. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present invention, and aperson of ordinary skill in the art may still derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a schematic diagram of an eCCE division according to anembodiment of the present invention;

FIG. 2 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 1 of the present invention;

FIG. 3 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 2 of the present invention;

FIG. 4 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 3 of the present invention;

FIG. 5 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 4 of the present invention;

FIG. 6 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 5 of the present invention;

FIG. 7 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 6 of the present invention;

FIG. 8A is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 7 of the present invention;

FIG. 8B is a schematic diagram showing physical resource mapping on aPDCCH according to an embodiment of the present invention;

FIG. 9A is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 8 of the present invention;

FIG. 9B and FIG. 9C are examples of allocating a DMRS port to acandidate E-PDCCH;

FIG. 10 is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 9 of the present invention;

FIG. 11 is a schematic structural diagram of a base station according toEmbodiment 10 of the present invention;

FIG. 12 is a schematic structural diagram of a user equipment accordingto Embodiment 11 of the present invention;

FIG. 13 is a schematic structural diagram of a base station according toEmbodiment 12 of the present invention;

FIG. 14 is a schematic structural diagram of a user equipment accordingto Embodiment 13 of the present invention;

FIG. 15 is a schematic structural diagram of a base station according toEmbodiment 14 of the present invention;

FIG. 16 is a schematic structural diagram of a user equipment accordingto Embodiment 15 of the present invention;

FIG. 17 is a schematic diagram of physical resources according toEmbodiment 16 of the present invention;

FIG. 18 is a first schematic diagram of an aggregation level andreference signal port correspondence according to Embodiment 16 of thepresent invention;

FIG. 19 is a second schematic diagram of an aggregation level andreference signal port correspondence according to Embodiment 16 of thepresent invention;

FIG. 20 is a third schematic diagram of an aggregation level andreference signal port correspondence according to Embodiment 16 of thepresent invention; and

FIG. 21 is a schematic diagram describing a start position according toEmbodiment 16 of the present invention.

DESCRIPTION OF EMBODIMENTS

The following clearly and completely describes the technical solutionsin the embodiments of the present invention with reference to theaccompanying drawings in the embodiments of the present invention.Apparently, the described embodiments are a part rather than all of theembodiments of the present invention. All other embodiments obtained bya person of ordinary skill in the art based on the embodiments of thepresent invention without creative efforts shall fall within theprotection scope of the present invention.

It should be understood that technical solutions of the presentinvention may be applied to various communications systems, for example,a GSM (Global System of Mobile communication) system, a CDMA (CodeDivision Multiple Access) system, a WCDMA (Wideband Code DivisionMultiple Access) system, a GPRS (General Packet Radio Service) system,an LTE (Long Term Evolution) system, an LTE-A (Advanced long termevolution) system, a UMTS (Universal Mobile Telecommunication System),and the like, which are not limited in the embodiments of the presentinvention, but for convenience of description, the embodiments of thepresent invention will be described by using an LTE system network as anexample.

The embodiments of the present invention may be applied to wirelessnetworks under different standards. A radio access network may includedifferent network elements in different systems. For example, networkelements of a radio access network in LTE and LTE-A include an eNB(Evolved Node B, evolved base station), while network elements of aradio access network in WCDMA includes an RNC (Radio Network Controller)and a base station Node B. Similarly, a WiMax (WorldwideInteroperability for Microwave Access) and other wireless networks mayalso use solutions similar to those in the embodiments of the presentinvention, but a relevant module in a base station system may bedifferent, which is not limited in the embodiments of the presentinvention, but for convenience of description, the following embodimentswill be described by using an eNodeB as an example.

It should be further understood that, in the embodiments of the presentinvention, a user equipment (UE) includes but is not limited to a mobilestation (MS), a mobile terminal, a mobile telephone, a handset, portableequipment, or the like. The user equipment may communicate with one ormore core networks through a radio access network (RAN; for example, theuser equipment may be a mobile phone (or called a “cellular” phone), acomputer with a radio communication function, or the like; and the userequipment may also be a portable, pocket-sized, handheld,computer-embedded, or vehicle-mounted mobile device.

FIG. 1 is a schematic diagram of an eCCE division according to anembodiment of the present invention. Referring to FIG. 1, after REsoccupied by Cell-specific reference signals (CRS), REs occupied by alater compatible control channel (for example, a legacy PDCCH) and REsoccupied by a reference signal of an E-PDCCH are excluded, each PRB pairmay be divided into 4 eCCEs. FIG. 1 shows a possible division method.The embodiment according to the present invention is not limited to thiseCCE division method, and does not limit that all eCCEs should have thesame number of REs. An E-PDCCH and a PDSCH are multiplexed in an FDMmode in a data area of a subframe. Transmission of an E-PDCCH is formedby two parts, that is, a reference signal part and a data symbol part.

According to an E-PDCCH mapping mode, E-PDCCHs may be classified intolocalized E-PDCCHs and distributed E-PDCCHs. A localized E-PDCCH ismapped in one PRB pair or adjacent PRB pairs in a centralized way, sothat a base station can select, according to a channel state report of aUE, a PRB pair in a better channel condition to send the E-PDCCH, so asto obtain a frequency scheduling gain. A distributed E-PDCCH isdispersed and mapped to multiple PRB pairs, so as to obtain a frequencydiversity benefit. The embodiment according to the present invention isdescribed by using a localized E-PDCCH as an example.

The foregoing problem that a UE judges a start position of an E-PDCCHincorrectly may be solved by adding a filling bit, for example, byfinding, according to sizes of different E-PDCCH formats and numbers ofCCEs of different CCE aggregations, sizes of all E-PDCCHs that arepossible to cause unclearness of a feedback information resource, andmaking a list. If a base station detects that the quantity of originalbits of an E-PDCCH that needs to be sent meets any one in the abovelist, the base station will add a zero behind the original bits of theE-PDCCH. The E-PDCCH corrected by adding a zero prevents the mentionedproblem that different eCCEs transmit same encoded E-PDCCH information.However, this method increases feedback overhead.

In addition, although the method of adding a filling bit solves theproblem that a UE judges a start position of an E-PDCCH incorrectly, aproblem cannot be avoided that the UE identifies an aggregation level ofthe E-PDCCH incorrectly. An E-PDCCH formed by 4 eCCEs is still used asan example. As a filling bit is added, it is impossible for the UE todetect an E-PDCCH at aggregation level 2 on the third eCCE and thefourth eCCE, but still possible that the UE detect an E-PDCCH ataggregation level 2 on the first eCCE and the second eCCE. As theE-PDCCH is sent in a data area of a subframe, and is multiplexed with aPDSCH based on FDM, if the aggregation level detection is incorrect,transmission of the PDSCH will possibly be affected. For example, it isassumed that one RBG has 3 PRB pairs, and one PRB pair has two eCCEs;that the base station sends an E-PDCCH at aggregation level 4 to a UE,which occupies 4 eCCEs of PRB pairs numbered 0 and 1 in RBG0; and thatresources allocated to the PDSCH are RBG0 and RBG1, where resources inRBG0 other than those for the E-PDCCH, can be used to transmit thePDSCH, which is to say, PDSCH resources that the base station allocatesare PRB pairs numbered 2, 3, 4 and 5. During E-PDCCH blind detection ata UE end, if the UE detects an E-PDCCH at aggregation level 2 on a PRBpair numbered 0, the UE regards that the PDSCH occupies PRB pairsnumbered 1, 2, 3, 4 and 5, thereby causing an incorrect PDSCH reception.In addition, a similar problem will also occur when an E-PDCCH and aPDSCH are multiplexed in a same PRB pair.

Embodiment 1

FIG. 2 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 1 of the present invention.The method in FIG. 2 may be executed by a base station.

210: A base station maps, according to an order of OFDM symbols used byan E-PDCCH of a UE, the E-PDCCH sequentially to REs used to transmit theE-PDCCH in each OFDM symbol.

For example, each E-PDCCH may include L (L=1, 2, 4 or 8) eCCEs; that isto say, REs used by the E-PDCCH may be divided into L eCCEs. Assumingthat OFDM symbols used by the E-PDCCH of the UE are symbols from then^(th) symbol to the m^(th) symbol, when physical resource mapping isperformed, according to an ascending order of indexes the OFDM symbols,a first part of modulation symbols of the E-PDCCH may be firstly mappedto REs used to transmit the E-PDCCH in the n^(th) symbol, and then asecond part of symbols may be mapped to REs used to transmit the E-PDCCHin the (n+1)^(th) symbol, and so on, till a last part of modulationsymbols are finally mapped to REs used to transmit the E-PDCCH in them^(th) symbol. Certainly, the embodiment of the present invention is notlimited thereto; for example, another order (for example, a descendingorder of indexes of the OFDM symbols or other specific orders) may alsobe used to perform physical resource mapping.

220: The base station sends the E-PDCCH to the UE by using the REs,where the E-PDCCH and a PDSCH invoked by the E-PDCCH arefrequency-division multiplexed.

For example, that the E-PDCCH and a PDSCH invoked by the E-PDCCH arefrequency-division multiplexed means that an E-PDCCH and a PDSCH inLTE11 are frequency-division multiplexed on REs of data part.

In the embodiment of the present invention, the E-PDCCH can be mapped,according to the order of OFDM symbols used by the E-PDCCH of the UE,sequentially to the REs used to transmit the E-PDCCH in each OFDMsymbol, so that, for candidate E-PDCCHs at a same start eCCE butdifferent aggregation levels, different eCCEs will not include E-PDCCHmodulation symbols of a same index, thereby avoiding that the UE judgesa start position of the E-PDCCH incorrectly. In addition, a problem thatE-PDCCHs at a same start position but different aggregation levels aremixed up is also solved.

In 210, when the E-PDCCH is mapped sequentially to the REs used totransmit the E-PDCCH in each OFDM symbol, in each OFDM symbol, theE-PDCCH may be sequentially mapped, according to an order of L eCCEsallocated to the E-PDCCH, to REs occupied by the L eCCEs in the OFDMsymbol, where L is an integer.

For example, before physical resource mapping is performed, REs that canbe used to transmit the E-PDCCH in a PRB pair may be firstly dividedinto multiple eCCEs. Another division method is to disperse REs of eacheCCE to all OFDM symbols of a data part with limitation to a part ofsubcarriers of the PRB pair, or disperse the REs of each eCCE to allOFDM symbols of the data part and subcarriers of the PRB pair. Underthis situation, if the E-PDCCH is sequentially mapped, according to theorder of L eCCEs allocated to the E-PDCCH, to REs occupied by the LeCCEs in the OFDM symbol, it can be ensured that, for candidate E-PDCCHsat a same start eCCE but different aggregation levels, different eCCEswill not have E-PDCCH modulation symbols of a same index.

In 210, when the E-PDCCH is mapped sequentially to the REs used totransmit the E-PDCCH in each OFDM symbol, in each OFDM symbol,modulation symbols of the e-PDCCH with index numbers of

$j_{0} + {\sum\limits_{q = 0}^{l - 1}\; N_{q}} + \left\lbrack {0,\ldots \mspace{14mu},{N_{l} - 1}} \right\rbrack$

may be mapped, according to the order of the L eCCEs allocated to theE-PDCCH, sequentially to REs of a set R_(l), where the set R_(l) is aset of REs occupied by the l^(th) eCCE among the L eCCEs included in theE-PDCCH, j₀ is a start position of the modulation symbols of the e-PDCCHmapped in the OFDM symbol, N_(l) is the quantity of the REs in the setR_(l), and N_(l), j₀, l and q are integers.

For example, an E-PDCCH at aggregation level L may include L eCCEs, andhave a modulation symbol sequence S_(j), where j=0, . . . J−1, where Jis the total number of REs of the L eCCEs included in the E-PDCCH, and jis an index number of an E-PDCCH modulation symbol. According to theembodiment of the present invention, an E-PDCCH sequence S_(j) may bemapped sequentially to the REs used to transmit the E-PDCCH in each OFDMsymbol.

In 210, when the E-PDCCH is mapped sequentially to the REs used totransmit the E-PDCCH in each OFDM symbol, in each OFDM symbol, the basestation maps, according to an order of subcarriers, the E-PDCCHsequentially to REs occupied by L eCCEs allocated to the E-PDCCH.

In 210, when the E-PDCCH is mapped sequentially to the REs used totransmit the E-PDCCH in each OFDM symbol, in each OFDM symbol,modulation symbols of the e-PDCCH with index numbers of j₀+[0, . . . ,N−1] may be mapped sequentially to REs of a set R, where j₀ is a startposition of modulation symbols of the E-PDCCH mapped in the OFDM symbol,the set R is a set of REs occupied by L eCCEs included in the E-PDCCH inthe OFDM symbol, N is the quantity of the REs in set R, and N and j₀ areintegers.

Embodiment 2

FIG. 3 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 2 of the present invention.The method in FIG. 3 is executed by a UE. The method in FIG. 3corresponds to the method in FIG. 2, and detailed descriptions here areomitted appropriately.

310: The UE receives a downlink subframe from a base station.

320: The UE extracts, in a blind detection process according to an orderof OFDM symbols used by a candidate E-PDCCH in the downlink subframe,modulation symbols of the candidate E-PDCCH sequentially from REs usedto transmit the candidate E-PDCCH in each OFDM symbol, and performsdecoding and CRC check on the candidate E-PDCCH, where the E-PDCCH ofthe UE and a PDSCH invoked by the E-PDCCH of the UE arefrequency-division multiplexed.

In the embodiment of the present invention, modulation symbols of thecandidate E-PDCCH can be obtained, according to an order of OFDM symbolsused by a candidate E-PDCCH of the UE, sequentially from REs used totransmit the E-PDCCH in each OFDM symbol, so that, for candidateE-PDCCHs at a same start eCCE but different aggregation levels,different eCCEs will not include a same E-PDCCH modulation symbol,thereby avoiding a problem that the UE judges a start position of theE-PDCCH incorrectly, and solves a problem that E-PDCCHs at a same startposition but different aggregation levels are mixed up.

In 320, when the UE uses, in the blind detection process, the order ofOFDM symbols used by the candidate E-PDCCH, in each OFDM symbol, the UEmay extract, according to an order of L eCCEs allocated to the candidateE-PDCCH, the modulation symbols of the candidate E-PDCCH sequentiallyfrom REs occupied by the L eCCEs in the OFDM symbol, where L is aninteger.

In 320, when the UE uses, in the blind detection process, the order ofOFDM symbols used by the candidate E-PDCCH, in each OFDM symbol, the UEmay extract modulation symbols of the candidate E-PDCCH and with indexnumbers of

$j_{0} + {\sum\limits_{q = 0}^{l - 1}\; N_{q}} + \left\lbrack {0,\ldots \mspace{14mu},{N_{l} - 1}} \right\rbrack$

from REs of a set R_(l), where the set R_(l) is a set of REs occupied bythe l^(h) eCCE among the L eCCEs included in the candidate E-PDCCH inthe OFDM symbol, j₀ is a start position of the modulation symbols of thecandidate E-PDCCH mapped in the OFDM symbol, N_(l) is the quantity ofthe REs in the set R_(l), and N_(l), j₀, l and q are integers.

In 320, when the UE uses, in the blind detection process, the order ofOFDM symbols used by the candidate E-PDCCH, in each OFDM symbol, the UEmay extract, according to an order of subcarriers, modulation symbols ofthe candidate E-PDCCH from REs occupied by the L eCCEs allocated to thecandidate E-PDCCH.

In 320, when the UE uses, in the blind detection process, the order ofOFDM symbols used by the candidate E-PDCCH, in each OFDM symbol, the UEmay extract modulation symbols of the candidate E-PDCCH and with indexnumbers of j₀+[0, . . . , N−1] from REs of a set R, where j₀ is a startposition of the modulation symbols of the candidate E-PDCCH mapped inthe OFDM symbol, the set R is a set of REs occupied by L eCCEs andincluded in the candidate E-PDCCH in the OFDM symbol, N is the quantityof the REs in the set R, and N and j₀ are integers.

Embodiment 3

FIG. 4 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 3 of the present invention.The method in FIG. 4 is executed by a base station.

410: The base station determines a reference signal port according to anaggregation level of an E-PDCCH of a UE, where E-PDCCHs at differentaggregation levels correspond to different reference signal ports, andthe aggregation level indicates the quantity of eCCEs included in theE-PDCCH.

420: The base station sends the E-PDCCH to the UE in a subframe, andsends a reference signal of the E-PDCCH to the UE by using thedetermined reference signal port, where the E-PDCCH and a PDSCH invokedby the E-PDCCH are frequency-division multiplexed.

For example, the reference signal may be a DMRS, and the referencesignal port may be a DMRS port. Correspondence between E-PDCCHs atdifferent eCCE aggregation levels and DMRS ports that the E-PDCCHs usemay be notified by using signaling, or may be determined by using animplicit method, which means that a signaling notification is notneeded, but some parameters, such as a cell identity, a UE identity andan aggregation level and the like are used to determine thecorrespondence. Different PRB pairs may have same correspondence, ordifferent correspondence may be defined for each PRB pair. Thecorrespondence may be cell-specific; for example, the base station maynotify all UEs in a cell by using broadcast signaling, which means thatall the UEs in the cell run according to same correspondence. Thecorrespondence may also be UE-specific; for example, the base stationmay notify a specific UE by using RRC signaling, which means thatdifferent UEs may have different correspondence.

For example, in LTE11, corresponding to candidate E-PDCCHs ataggregation levels 1, 2, 4 and 8, the reference signal is sent bysequentially using DMRS ports 7, 8, 9 and 10.

According to the embodiment of the present invention, reference signalsof E-PDCCHs at different eCCE aggregation levels can be sent by usingdifferent DMRS ports, so that the UE can demodulate an E-PDCCH at eachaggregation level correctly according to a special DMRS reference signalof the E-PDCCH, thereby avoiding a problem that the UE judges a startposition of the E-PDCCH incorrectly, and solving a problem that E-PDCCHsat a same start position but different aggregation levels are mixed up.

According to the embodiment of the present invention, an E-PDCCH ataggregation level L=2^(m-1) corresponds to a reference signal port witha port number 7+(m+σ)mod P, where m=1, 2, 3, 4, σ is 0 or a UE-specificparameter or a cell-specific parameter, and P is the quantity ofavailable reference signal ports for the E-PDCCH, and P=4.

Optionally, that E-PDCCHs at different aggregation levels correspond todifferent reference signal ports may include that, E-PDCCHs at differentaggregation levels, among a part or all of aggregation levelscorresponding to E-PDCCHs of the UE, correspond to different referencesignal ports.

Optionally, the determining, by the base station, a reference signalport according to the aggregation level of the physical downlink controlchannel E-PDCCH of the UE, where E-PDCCHs at different aggregationlevels correspond to different reference signal ports may specificallybe: selecting, by the base station according to the aggregation level ofthe physical downlink control channel E-PDCCH of the UE, one or morereference signal ports from a reference signal port set corresponding tothe aggregation level as a reference signal port corresponding to theaggregation level, where reference signal ports selected for E-PDCCHs atdifferent aggregation levels are different.

According to the embodiment of the present invention, in 410, it isacceptable that only E-PDCCHs at a same start position in the subframebut different aggregation levels correspond to different referencesignal ports. In other words, without depending on the aggregationlevel, E-PDCCHs with different start positions may correspond to a samereference signal port.

Optionally, as another embodiment, the method in FIG. 4 furtherincludes: configuring, by the base station, correspondence between eCCEsin the subframe and the reference signal ports, so that, according tothe correspondence between eCCEs in the subframe and the referencesignal ports, enabling E-PDCCHs at a same start position but differentaggregation levels in the subframe correspond to different referencesignal ports.

Further, the at a same start position in the subframe may include: at asame start position in a same physical resource block pair or differentphysical resource block pairs.

Further, E-PDCCHs, corresponding to different user equipments UEs, at asame aggregation level, and occupying a same physical resource,correspond to different reference signal ports.

The correspondence between eCCEs in the subframe and the referencesignal ports includes: the i^(th) eCCE in the subframe corresponds to areference signal port 7+(i+σ)mod P, where i is an index of the eCCE inthe subframe, σ is 0 or a UE-specific parameter or a cell-specificparameter, and P is the quantity of available reference signal ports,and P=4, and i is an integer; in 410, the base station sends a referencesignal of the E-PDCCH at aggregation level L=2^(m-1) by using areference signal port corresponding to the m^(th) eCCE in the E-PDCCH ataggregation level L=2^(m-1), where m=1, 2, 3, 4.

Embodiment 4

FIG. 5 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 4 of the present invention.The method in FIG. 5 is executed by a UE. The method in FIG. 5corresponds to the method in FIG. 4, and detailed descriptions here areomitted appropriately.

510: The UE receives a reference signal of a candidate E-PDCCH from areference signal port in a subframe, where candidate E-PDCCHs atdifferent aggregation levels correspond to different reference signalports, and the aggregation level indicates the quantity of eCCEsincluded in the candidate E-PDCCH.

The UE receives, from a reference signal port in a subframe, a referencesignal of a candidate physical downlink control channel E-PDCCH sent bya base station, where candidate E-PDCCHs at different aggregation levelscorrespond to different reference signal ports, and the aggregationlevel indicates the quantity of control channel elements included in thecandidate E-PDCCH.

520: The UE performs channel estimation according to the referencesignal, so as to demodulate the candidate E-PDCCH.

Further, optionally, the E-PDCCH of the UE and a PDSCH invoked by theE-PDCCH of the UE are frequency-division multiplexed.

The UE performs channel estimation according to the reference signal, soas to demodulate the candidate E-PDCCH, where the candidate E-PDCCH anda physical downlink shared channel PDSCH invoked by the candidateE-PDCCH are frequency-division multiplexed.

For example, assuming that the base station sends an E-PDCCH ataggregation level 2 and sends a reference signal by using DMRS port 8,when blindly detecting each candidate E-PDCCH at aggregation level 1,the UE tries to perform channel estimation based on DMRS port 7 anddemodulate the E-PDCCH; however, in fact, the base station does not sendthe reference signal to the UE by using DMRS port 7; it is quite clearthat the demodulated output is some random noise, so that CRC check isnot possible to be successful, thereby avoiding that the UE mixes upcandidate E-PDCCHs at different aggregation levels.

According to the embodiment of the present invention, reference signalsof E-PDCCHs at different eCCE aggregation levels can be sent by usingdifferent DMRS ports, thereby avoiding a problem that the UE judges astart position of the E-PDCCH incorrectly, and solving a problem thatE-PDCCHs at a same start position but different aggregation levels aremixed up.

According to the embodiment of the present invention, an E-PDCCH ataggregation level L=2^(m-1) corresponds to a reference signal port witha port number 7+(m+σ)mod P, where m=1, 2, 3, 4, σ is 0 or a UE-specificparameter or a cell-specific parameter, and P is the quantity ofavailable reference signal ports for the E-PDCCH, and P=4.

Optionally, as another embodiment, in 510, it is acceptable that onlyE-PDCCHs at a same start position but different aggregation levelscorrespond to different reference signal ports. In other words, withoutdepending on the aggregation level, E-PDCCHs with different startpositions may correspond to a same reference signal port.

The method in FIG. 5 further includes: configuring, by the UE,correspondence between eCCEs in the subframe and the reference signalports, so that, according to the correspondence between eCCEs in thesubframe and the reference signal ports, enabling E-PDCCHs at a samestart position but different aggregation levels in the subframecorrespond to different reference signal ports.

The correspondence between the eCCEs in the subframe and the differentreference signal ports includes: the i^(th) eCCE in the subframecorresponds to a reference signal port 7+(i+σ) mod P, where i is anindex of the eCCE in the subframe, σ is 0 or a UE-specific parameter ora cell-specific parameter, and P is the quantity of available referencesignal ports, and P=4, and i is an integer; in 510, the UE may receive areference signal of an E-PDCCH at aggregation level L=2^(m-1) from areference signal port corresponding to the m^(th) eCCE in the E-PDCCH ataggregation level L=2^(m-1), where m=1, 2, 3, 4.

Optionally, that candidate E-PDCCHs at different aggregation levelscorrespond to different reference signal ports may specifically be:selecting, by the UE, according to the aggregation level of thecandidate E-PDCCH of the UE, one or more reference signal ports from areference signal port set corresponding to the aggregation level as areference signal port corresponding to the aggregation level, wherecandidate E-PDCCHs at different aggregation levels correspond todifferent reference signal ports.

Further, that candidate E-PDCCHs at different aggregation levelscorrespond to different reference signal ports may include: thatcandidate E-PDCCHs at a same start position but different aggregationlevels in the subframe correspond to different reference signal ports.

Optionally, that candidate E-PDCCHs at different aggregation levelscorrespond to different reference signal ports may include:

that candidate E-PDCCHs at different aggregation levels, among a part orall of aggregation levels corresponding to candidate E-PDCCHs of the UE,correspond to different reference signal ports.

Embodiment 5

FIG. 6 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 5 of the present invention.The method in FIG. 6 is executed by a base station.

610: The base station sends a reference signal of the E-PDCCH by using afirst reference signal port v.

620: The base station sends a reference signal of the PDSCH by using atleast one second reference signal port.

630: The base station determines not to use a second reference signalport p(v) to send the reference signal of the PDSCH, so that a referencesignal port of the E-PDCCH and a reference signal port of the PDSCH areprocessed based on orthogonal time extensions with different lengths,where the E-PDCCH and the PDSCH are frequency-division multiplexed, thefirst reference signal port may be one of the at least one secondreference signal port, and v and p(v) are serial numbers of thereference signal ports.

For example, LTE release 11 supports multiplexing of an E-PDCCH and aPDSCH; in order that a DMRS port with respect to an E-PDCCH is processedbased on an orthogonal time extension with a length of 2, and also that.when a PDSCH with a rank of 5, 6 or 7 is scheduled by the E-PDCCH, aDMRS port with respect to a PDSCH is processed based on an orthogonaltime extension with a length of 4, the present invention proposes thefollowing limitation on the DMRS ports for the PDSCH; that is to say,when a DMRS port occupied by the E-PDCCH of the UE is v, a DMRS portp(v) is defined not to be used to demodulate the PDSCH, or, another DMRSport is needed to replace the p(v), so that a reference signal port ofthe E-PDCCH and a reference signal port of the PDSCH are processed basedon orthogonal time extensions with different lengths, and that theE-PDCCH and the PDSCH can be multiplexed normally.

According to the embodiment of the present invention, when sending thereference signal of the PDSCH by using a reference signal port resultsthat the reference signal ports of the E-PDCCH and the PDSCH cannot beprocessed based on orthogonal time extensions with different lengths,the reference signal port may be not used to send the reference signalof the PDSCH, so that the reference signal of the PDSCH and thereference signal of the E-PDCCH are multiplexed normally.

According to the embodiment of the present invention, the at least onesecond reference signal port includes at least one of PDSCH referencesignal ports 7, 8, 9, 10, 11, 12, 13 and 14 defined in LTE release 10,the first reference signal port includes an E-PDCCH reference signalport 7, 8, 9, or 10 defined in LTE release 10, and

${p(v)} = \left\{ {\begin{matrix}{11,{v = 7}} \\{13,{v = 8}} \\{12,{v = 9}} \\{14,{v = 10}}\end{matrix}.} \right.$

In 620, when a rank R of the PDSCH is less than or equal to 4, the basestation may send the reference signal of the PDSCH by using a PDSCHreference signal port defined in LTE release 10.

Optionally, as another embodiment, when the rank of the PDSCH is one of5, 6 and 7, the base station sends the reference signal of the PDSCH byusing a PDSCH reference signal port defined in LTE release 10, and whenneeding to send the reference signal of the PDSCH by using the secondreference signal port p(v), replaces the reference signal port p(v) withanother available reference signal port among the PDSCH reference signalports, where R is an integer.

According to the embodiment of the present invention, when a rank R ofthe PDSCH is less than or equal to 4, the base station sends thereference signal of the PDSCH by using R reference signal ports7+(v−7+r)mod 4 starting from the reference signal port v, where r=0, . .. , R−1, and R is an integer.

Optionally, as another embodiment, when the rank R of the PDSCH is equalto one of 5, 6 and 7, the base station sends the reference signal of thePDSCH by using R reference signal ports 7+(v−7+r) mod 8 starting fromthe reference signal port v, and when the R reference signal portsinclude the reference signal port p(v), replaces the reference signalport p(v) with another reference signal port among the PDSCH referencesignal ports, where r=0, . . . , R−1.

Optionally, as another embodiment, when a rank R of the PDSCH is equalto 3 or 4, the base station may send the reference signal of the PDSCHby using R reference signal ports 7+(v−7+r) mod 4 starting from thereference signal port v, where R is an integer, r=0, . . . , R−1; andwhen the rank R of the PDSCH is equal to 2, the base station sends thesend the reference signal of the PDSCH by using reference signal ports vand v+(−1)^((v-7)mod 2).

Embodiment 6

FIG. 7 is a schematic flowchart of a method for transmitting downlinkcontrol information according to Embodiment 6 of the present invention.The method in FIG. 7 is executed by a UE. The method in FIG. 7corresponds to the method in FIG. 6, and detailed descriptions here areomitted appropriately.

710: The UE receives a reference signal of an E-PDCCH which is sent by abase station by using a first reference signal port v and a referencesignal of a PDSCH which is sent by the base station by using at leastone second reference signal port, where the PDSCH is invoked by theE-PDCCH.

720: The UE performs channel estimation by using the reference signal ofthe E-PDCCH, so as to demodulate the E-PDCCH, and performs channelestimation by using the reference signal of the PDSCH, so as todemodulate the PDSCH.

730: The base station determines not to use the reference signal of thePDSCH sent by a second reference signal port p(v) to perform channelestimation, so that a reference signal port of the E-PDCCH and areference signal port of the PDSCH are processed based on orthogonaltime extensions with different lengths, where the E-PDCCH and the PDSCHare frequency-division multiplexed, the first reference signal port maybe one of the at least one second reference signal port, and v and p(v)are serial numbers of the reference signal ports.

According to the embodiment of the present invention, when sending thereference signal of the PDSCH by using a reference signal port resultsthat the reference signal ports of the E-PDCCH and the PDSCH cannot beprocessed according to orthogonal time extensions with differentlengths, the reference signal port may be not used to send the referencesignal of the PDSCH, so that the reference signal of the PDSCH and thereference signal of the E-PDCCH are multiplexed normally.

According to the embodiment of the present invention, the at least onesecond reference signal port includes at least one of PDSCH referencesignal ports 7, 8, 9, 10, 11, 12, 13 and 14 defined in LTE release 10;that is to say, the second reference signal port includes the PDSCHreference signal ports 7, 8, 9, 10, 11, 12, 13 or 14 defined in LTErelease 10, the first reference signal port includes an E-PDCCHreference signal port 7, 8, 9, or 10 defined in LTE release 10, and

${p(v)} = \left\{ {\begin{matrix}{11,{v = 7}} \\{13,{v = 8}} \\{12,{v = 9}} \\{14,{v = 10}}\end{matrix}.} \right.$

According to the embodiment of the present invention, when a rank R ofthe PDSCH is less than or equal to 4, the UE performs channel estimationby using a reference signal of the PDSCH sent by a PDSCH referencesignal port defined in LTE release 10.

According to the embodiment of the present invention, when the rank R ofthe PDSCH is one of 5, 6 and 7, the UE may perform channel estimation byusing a reference signal of the PDSCH sent by a PDSCH reference signalport defined in LTE release 10, and when needing to perform channelestimation by using the reference signal of the PDSCH sent by the secondreference signal port p(v), replaces the reference signal port p(v) withanother available reference signal port among the PDSCH reference signalports to perform channel estimation.

Optionally, as another embodiment, when a rank R of the PDSCH is lessthan or equal to 4, the UE performs channel estimation by usingreference signals of the PDSCH sent by R reference signal ports7+(v−7+r) mod 4 starting from the reference signal port v, where r=0, .. . , R−1, and R is an integer; or, when the rank R of the PDSCH isequal to one of 5, 6 and 7, the UE performs channel estimation by usingreference signals of the PDSCH sent by R reference signal ports7+(v−7+r) mod 8 starting from the reference signal port v, and when theR reference signal ports include the reference signal port p(v),replaces the reference signal port p(v) with another reference signalport among the PDSCH reference signal ports to perform channelestimation, where r=0, . . . , R−1.

According to the embodiment of the present invention, when a rank R ofthe PDSCH is equal to 3 or 4, the UE performs channel estimation byusing reference signals of the PDSCH sent by R reference signal ports7+(v−7+r) mod 4 starting from the reference signal port v, where r=0, .. . , R−1; and when the rank of the PDSCH is equal to 2, the UE performschannel estimation by using reference signals of the PDSCH sent byreference signal ports v and v+(−1)^((v-7)mod 2).

With reference to a specific example, the following describes theembodiments of the present invention in more detail.

Embodiment 7

FIG. 8A is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 7 of the present invention.FIG. 8B is a schematic diagram showing physical resource mapping on aPDCCH according to an embodiment of the present invention. Embodiment 7elaborates one or more steps of the methods in Embodiment 1 andEmbodiment 2.

810: A base station performs CRC check code addition, scrambling,encoding and rate matching on downlink control information of a UE, soas to obtain modulation symbols of a PDCCH.

For example, scrambling may be performed on the downlink controlinformation of the UE by using 16-bit cyclic redundancy check (CRC) anda radio network temporary identity (RNTI), and encoding and ratematching is performed on the downlink control information of the UE byusing convolutional encoding with master code being 1/3 and a circularbuffering based rate, so as to obtain modulation symbols of a PDCCH.

820: The base station maps, according to an order of OFDM symbols usedby a PDCCH, the PDCCH sequentially to REs used to transmit the E-PDCCHin each OFDM symbol.

Before physical resource mapping is performed, REs that can be used totransmit the E-PDCCH in a PRB pair may be divided into several eCCEs.Here, a specific eCCE division method is not limited.

Specifically, for a localized E-PDCCH, a simple eCCE division method isto limit an eCCE to a part of subcarriers, for example, a divisionmethod in FIG. 1. Another method is to disperse REs of each eCCE to allsubcarriers and all OFDM symbols of a data part of the PRB pair, forexample, assuming that the quantity of REs available for the E-PDCCH inthe PRB pair is N, and the REs are divided into K eCCEs. Particularly,the K eCCEs may have an equal size, that is, └N/K┘; under thissituation, the quantity of REs that are not used is N mod K. In order tofully utilize all REs, and ensure that sizes of eCCEs divided in a PRBpair are as close as possible, a simple method is to allocate a size of┌N/K┐ to the first N mod K eCCEs, and allocate a size of └N/K┘ to othereCCEs. However, this method may cause uneven sizes of candidate E-PDCCHsat aggregation level 2; for example, assuming that K is equal to 4, andN mod K=2, and assuming that the first two eCCEs form a candidateE-PDCCH at aggregation level 2, while the last two eCCEs form anothercandidate E-PDCCH at aggregation level 2, a difference in the numbers ofREs between the two candidate E-PDCCHs is 2, but in fact, the twocandidate E-PDCCHs may possibly have an equal number of REs. Therefore,another method to allocate eCCE sizes is to map eCCEs with a size of┌N/K┐ in the PRB pair to discontinuous eCCE indexes, for example, todefine a size of an eCCE with an index of └k·K/(N mod K)┘ as ┌N/K┐,where k=0, . . . , N mod K−1, and define a size of other eCCEs as └N/K┘.

Similarly, for a distributed E-PDCCH, assuming that a total number ofavailable REs in a PRB pair of the distributed E-PDCCH is N, and the REsare divided into K eCCEs. Particularly, the K eCCEs may have an equalsize, that is, └N/K┘; under this situation, the quantity of REs that arenot used is N mod K. In order to fully utilize all REs, and ensure thatsizes of eCCEs divided in a PRB pair are as close as possible, a simplemethod is to allocate a size of ┌N/K┐ to the first N mod K eCCEs, andallocate a size of └N/K┘ to other eCCEs. Optionally, as anotherembodiment, eCCEs with a size of ┌N/K┐ may be mapped to discontinuouseCCE indexes, for example, to define a size of an eCCE with an index of└k·K/(N mod K)┘ as ┌N/K┐, where k=0, . . . , N mod K−1, and define asize of another eCCE as └N/K┘.

According to the embodiment of the present invention, an E-PDCCH ataggregation level L may include L eCCEs, and have a modulation symbolsequence S_(p) where j=0, . . . J−1, where J is a total number of REs ofthe L eCCEs included in the E-PDCCH. The base station performs physicalresource mapping on each E-PDCCH. The base station may, according to afrequency priority method, firstly map the E-PDCCH to REs occupied by LeCCEs allocated to the E-PDCCH on an OFDM symbol of the E-PDCCH, andthen map the E-PDCCH to REs occupied by the L eCCEs allocated to theE-PDCCH on a next OFDM symbol of the E-PDCCH.

Specifically, in an OFDM symbol, the E-PDCCH may be firstly mapped toREs occupied by an eCCE among the L eCCEs included in the E-PDCCH, andthen mapped to REs occupied by a next eCCE. Assuming that in an OFDMsymbol, a RE set occupied by the l^(th) eCCE among the L eCCEs includedin the E-PDCCH is R_(l), and the quantity of REs included in the set isN_(l), modulation symbols of the e-PDCCH with an index j within a range

$j_{0} + {\sum\limits_{q = 0}^{l - 1}\; N_{q}} + \left\lbrack {0,\ldots \mspace{14mu},{N_{l} - 1}} \right\rbrack$

are mapped sequentially to the REs of the set R_(l) according to anorder of eCCEs, where j₀ is a start position of the modulation symbolsof the E-PDCCH mapped in the OFDM symbol.

Optionally, as another embodiment, in an OFDM symbol, for REs of L eCCEsallocated to the E-PDCCH, eCCEs are not differentiated and mapping isperformed according to an order of subcarriers. Assuming that, in anOFDM symbol, a RE set occupied by L eCCEs included in an E-PDCCH is R,and a total number of REs included in the set is N, modulation symbolsof the e-PDCCH with an index j within a range j₀+[0, . . . , N−1] aremapped sequentially to the REs of the set R, where j₀ is a startposition of the modulation symbols of the E-PDCCH mapped in the OFDMsymbol.

Referring to FIG. 8B, FIG. 8B shows physical resource mapping of anE-PDCCH at aggregation level 1 and physical resource mapping of anE-PDCCH at aggregation level 2. It can be seen from FIG. 8B that, amodulation symbol of an E-PDCCH at aggregation level 2 mapped in eCCE0is almost completely different with a modulation symbol of an E-PDCCH ataggregation level 1 mapped in eCCE0 or eCCE1.

830: The base station sends the E-PDCCH to the UE by using a RE, andsends the PDSCH scheduled by the E-PDCCH to the UE.

840: After receiving a downlink subframe from the base station, the UEextracts, in a blind detection process according to an order of OFDMsymbols used by a candidate E-PDCCH, modulation symbols of the candidateE-PDCCH sequentially from REs used to transmit the candidate E-PDCCH ineach OFDM symbol.

For a PDSCH and an E-PDCCH transmitted in a subframe, the UE firstlyneeds to blindly detect the E-PDCCH, that is, to detect, from allcandidate E-PDCCHs in a search space of the UE, the E-PDCCH that thebase station sends to the UE. For example, the UE performs channelestimation based on a reference signal part, and performs demodulation,decoding and CRC check and like operations on a data symbol part, so asto obtain downlink control information (DCI) of the UE transmitted onthe E-PDCCH.

Referring to FIG. 8B again, assuming that the base station actuallysends an E-PDCCH at aggregation level 2 by using eCCE0 and eCCE1, it isimpossible that the UE detect an E-PDCCH at aggregation level 1 on eCCE0and eCCE1. Therefore, according to the method in the embodiment of thepresent invention, the foregoing problem that a start position of theE-PDCCH is judged incorrectly and the problem that E-PDCCHs at a samestart position but different aggregation levels are mixed up are bothsolved.

850: If detecting its own E-PDCCH, the UE demodulates a correspondingPDSCH according to the downlink control information in the E-PDCCH, andfeeds back in the uplink according to whether the PDSCH demodulation iscorrect.

For example, if the PDSCH is demodulated correctly, the UE feeds back anacknowledgement (ACK) message to the eNodeB, indicating that the UE hasalready correctly received data sent by the eNodeB, and the eNodeB maytransmit new data. Otherwise, the UE feeds back anegative-acknowledgement (NACK) message to the eNodeB, indicating thatthe data has not been received correctly, and the eNodeB needs toretransmit the data. Another situation is that the E-PDCCH has not beendetected correctly, so that the UE assumes that no data is scheduled tothe UE, and does not feed back anything in an uplink, which meansdiscontinuous transmission (DTX).

Embodiment 8

FIG. 9A is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 8 of the present invention.Embodiment 8 elaborates one or more steps of the methods in Embodiment 3and Embodiment 4.

According to the embodiment of the present invention, a localizedE-PDCCH is used as an example for description. As a reference signal ofan E-PDCCH is dedicated to one UE, a reference signal port (that is aDMRS port) and eCCEs occupied by the E-PDCCH both need to be defined ina design of an E-PDCCH search space. According to the embodiment of thepresent invention, reference signals of E-PDCCHs at different eCCEaggregation levels can be sent by using different DMRS ports, so as toprevent the UE from mixing up the E-PDCCHs at different eCCE aggregationlevels.

910: A base station performs CRC check code addition, scrambling,encoding and rate matching on downlink control information of a UE, soas to obtain modulation symbols of a PDCCH. 910 in FIG. 9 is similar to810 in FIG. 8, and is not described here any further.

920: The base station maps an E-PDCCH to a physical source, anddetermines a reference signal port according to an aggregation level ofthe E-PDCCH of the UE, where E-PDCCHs at different aggregation levelscorrespond to different reference signal ports.

Correspondence between E-PDCCHs at different eCCE aggregation levels andDMRS ports that the E-PDCCHs use may be notified by using signaling, ormay be determined by using an implicit method, which means that asignaling notification is not needed, but some parameters, such as acell identity, a UE identity and an aggregation level and the like areused to determine the correspondence. Different PRB pairs may have samecorrespondence, or different correspondence may be defined for each PRBpair. The correspondence may be cell-specific; for example, the basestation may notify all UEs in a cell by using broadcast signaling, whichmeans that all the UEs in the cell run according to same correspondence.The correspondence may also be UE-specific; for example, the basestation may notify a specific UE by using RRC signaling, which meansthat different UEs may have different correspondence.

For example, the quantity of DMRS ports available for an E-PDCCH is P;in LTE release 11, P may be equal to 4; that is to say, DMRS ports 7, 8,9 and 10 may be used as E-PDCCH reference signal ports. Therefore, for aUE, a DMRS port used by a candidate E-PDCCH at aggregation level L=2^(m)may be defined as 7+(m+σ)mod P, where σ is a fixed value, for example, σis equal to 0; or σ is a cell-specific parameter; or σ is a specificparameter for each transmission point in a cell in coordinatedmulti-point transmission; or σ is a UE-specific parameter. For example,for a UE, corresponding to candidate E-PDCCHs at aggregation levels 1,2, 4 and 8, the reference signal is sent sequentially by using DMRSports 7, 8, 9 and 10.

Optionally, as another embodiment, assuming that a problem that a startposition of an E-PDCCH is judged incorrectly has already been solved byusing another method, for example, by using a method of adding a fillingbit in LTE release 8, only a problem needs to be solved that E-PDCCHs ata same start position but different aggregation levels is mixed. Here,it is only necessary to allocate different DMRS ports to candidateE-PDCCHs at a same start eCCE but different aggregation levels to sendreference signals; that is to say, for candidate E-PDCCHs with differentstart eCCEs, a same DMRS port may be allocated to send referencesignals. Assuming that correspondence between each eCCE and a DMRS portis defined by using a method, the correspondence may be notified byusing signaling, but with a high overhead; or the correspondence may bedetermined by using an implicit method, which means that no signalingnotification is needed, but some parameters (such as a cell identity, aUE identity and an aggregation level and the like) are used to determinethe correspondence. Different PRB pairs may have same correspondence, ordifferent correspondence may be defined for each PRB pair. Thecorrespondence may be cell-specific; for example, the base station maynotify all UEs in a cell by using broadcast signaling, which means thatall the UEs in the cell run according to same correspondence. Thecorrespondence may also be UE-specific; for example, the base stationmay notify a specific UE by using RRC signaling, which means thatdifferent UEs may have different correspondence.

According to the embodiment of the present invention, in order toallocate different DMRS ports to candidate E-PDCCHs at a same startposition but different aggregation levels, eCCEs may be sorted firstly;for example, eCCEs in a PRB pair may be numbered firstly, and eCCEs in anext PRB pair may be numbered subsequently; that is to say, an eCCE withan index i corresponds to the (i mod K)^(th) eCCE in the └i/K┘^(th)E-PDCCH PRB pair, where K is the quantity of eCCEs divided in each PRBpair. The embodiment of the present invention is not limited to thisnumbering method.

Then, based on the eCCE numbering, a DMRS port corresponding to eacheCCE is defined sequentially; for example, when the quantity ofavailable DMRS ports is P, eCCEs may be defined to use reference signalsat the P DMRS ports sequentially and circularly. In LTE release 11, P isequal to 4; that is to say, DMRS ports 7, 8, 9 and 10 may be used asE-PDCCH reference signal ports. Therefore, for a UE, a DMRS portcorresponding to the i^(th) eCCE may be defined as 7+(i+σ)mod P, where σis a fixed value, for example, 0; optionally, σ is a cell-specificparameter; optionally, σ is a specific parameter specific to eachtransmission point in a cell in coordinated multi-point transmission;and optionally, σ is a UE-specific parameter.

Finally, based on the correspondence between eCCEs and DMRS ports, aDMRS port that an E-PDCCH at each aggregation level uses is defined, andit is ensured that candidate E-PDCCHs at a same start position butdifferent aggregation levels use different DMRS ports. For example, whenthe aggregation level is L=2^(m-1) (m=1, 2, 3, 4), each candidateE-PDCCH may be defined to use a DMRS port mapped to the m^(th) eCCE tosend a reference signal.

FIG. 9B and FIG. 9C are examples of allocating a DMRS port to acandidate E-PDCCH.

Referring to FIG. 9B, assuming that one RBG includes two PRB pairs, andeach PRB pair is divided into 4 eCCEs, according to the foregoingmethod, for a UE, eCCEs use DMRS ports 7, 8, 9 and 10 sequentially andcircularly. For aggregation level 1, a DMRS port mapped to an eCCEincluded in a candidate E-PDCCH is used; for aggregation level 2, a DMRSport mapped to a second eCCE included in a candidate E-PDCCH is used,which means that DMRS ports 8 and 10 may be used; for aggregation level4, a DMRS port mapped to a third eCCE included in a candidate E-PDCCH isused, which means port 9 is always used; and for aggregation level 8, aDMRS port mapped to a fourth eCCE included in a candidate E-PDCCH isused, which means port 10 is always used. When a candidate E-PDCCHcrosses more than one PRB pair, a DMRS port determined according to theforegoing method is also configured to bear a reference signal onmultiple PRB pairs mapped to the candidate E-PDCCH, for example, whenthe aggregation level is 8.

Referring to FIG. 9C, assuming that one RBG includes three PRB pairs,and each PRB pair is divided into 3 eCCEs, according to the foregoingmethod, for a UE, it is still assumed that eCCEs use DMRS ports 7, 8, 9and 10 sequentially and circularly. For aggregation level 1, a DMRS portmapped to an eCCE included in a candidate E-PDCCH is used; foraggregation level 2, a DMRS port mapped to a second eCCE included in acandidate E-PDCCH is used, which means that DMRS ports 8 and 10 may beused; for aggregation level 4, a DMRS port mapped to a third eCCEincluded in a candidate E-PDCCH is used, which means port 9 is alwaysused; and for aggregation level 8, a DMRS port mapped to a fourth eCCEincluded in a candidate E-PDCCH is used, which means port 10 is alwaysused. When a candidate E-PDCCH crosses more than one PRB pair, a DMRSport determined according to the foregoing method is further configuredto bear a reference signal on multiple PRB pairs mapped to the candidateE-PDCCH, for example, when the aggregation level is 2, 4 and 8.

930: The base station sends the E-PDCCH to the UE in a subframe, andsends a PDSCH scheduled by the PDCCH to the UE.

When sending the E-PDCCH, the base station sends a reference signal ofthe E-PDCCH to the UE by using the determined reference signal port,where the E-PDCCH and the PDSCH invoked by the E-PDCCH arefrequency-division multiplexed; and E-PDCCHs at a same start positionbut different aggregation levels correspond to different referencesignal ports.

940: In a blind detection process, the UE performs channel estimationaccording to the reference signal, so as to demodulate the candidateE-PDCCH.

Assuming that the base station sends an E-PDCCH at aggregation level 2and sends a reference signal by using DMRS port 8, when blindlydetecting each candidate E-PDCCH at aggregation level 1, the UE tries toperform channel estimation based on DMRS port 7 and demodulate theE-PDCCH; however, in fact, the base station does not send the referencesignal to the UE by using DMRS port 7; it is quite clear that thedemodulated output is some random noise, so that CRC check is notpossible to be successful, thereby avoiding that the UE mixes upcandidate E-PDCCHs at different aggregation levels. This method alsosolves the foregoing problem that a start position of an E-PDCCH isjudged incorrectly and the problem that E-PDCCHs at a same startposition but different aggregation levels are mixed up.

950: If detecting its own E-PDCCH, the UE demodulates a correspondingPDSCH according to the downlink control information in the E-PDCCH, andfeeds back in the uplink according to whether the PDSCH demodulation iscorrect. 950 in FIG. 9 is similar to 850 in FIG. 8, and is not describedhere any further.

Embodiment 9

FIG. 10 is a schematic flowchart of a process for transmitting downlinkcontrol information according to Embodiment 9 of the present invention.Embodiment 9 elaborates one or more steps of the methods in Embodiment 5and Embodiment 6.

In order to support multiplexing of an E-PDCCH and a PDSCH, anotherproblem to be solved is how to configure reference signals of theE-PDCCH and the PDSCH. One situation is that the E-PDCCH and the PDSCHare multiplexed in one PRB pair, where because the reference signal ofthe E-PDCCH and the PDSCH are sent on a same PRB pair, the referencesignal of the E-PDCCH may possibly be used to demodulate the PDSCH.Another situation is that the E-PDCCH and the PDSCH are multiplexed indifferent PRB pairs of a same RBG; here, although a PRB pair where theE-PDCCH is located does not transmit the PDSCH, it is possible thatchannel estimation of the reference signal of the E-PDCCH is used toenhance, by means of interpolation, channel estimation accuracy of a PRBpair where the PDSCH is located. Under both the two situations, a methodfor multiplexing the reference signals of the E-PDCCH and the PDSCHneeds to be defined.

Specifically, when a rank of the PDSCH is one of 5, 6 and 7, a DMRS portof at least a part of data flows of the PDSCH is expanded in time byusing a walsh code with a length of 4. However, in order to ensurechannel estimation performance of an E-PDCCH, a reference signal of theE-PDCCH uses DMRS ports 7, 8, 9 and 10, where the four DMRS ports may beprocessed based on a time extension of walsh codes with a length of 2.Therefore, when the reference signals of the E-PDCCH and the PDSCH aremultiplexed, a problem needs to be solved that walsh codes used by theE-PDCCH and the PDSCH have different lengths.

In release 10, a maximum rank available for PDSCH transmission is 8; aPDSCH DMRS port is mapped to two RE sets bearing a reference signal, andthese two sets are multiplexed based on FDM/TDM, and may multiplex atmost four DMRS ports on each RE set. DMRS ports 7, 8, 11 and 13 aremultiplexed in a CMD multiplexing mode on a first RE set, while DMRSports 9, 10, 12 and 14 are multiplexed in a CMD multiplexing mode on asecond RE set.

Referring to Table 1, Table 1 shows walsh codes used by the foregoing 8DMRS ports respectively. Walsh codes of the four DMRS ports in the firstRE set are used as an example, the first two elements and the last twoelements of walsh codes of DMRS ports 7 and 8 are orthogonalrespectively, so that DMRS ports 7 and 8 can be processed based on anorthogonal time extension with a length of 2; the first two elements andthe last two elements of walsh codes of DMRS ports 7 and 13 are alsoorthogonal respectively, so that DMRS ports 7 and 13 can also beprocessed based on an orthogonal time extension with a length of 2.However, neither the first two elements nor the last two elements ofwalsh codes of DMRS ports 7 and 11 are orthogonal, but only an entiretyof the four elements is orthogonal; and therefore, the two ports canonly be processed based on an orthogonal time extension with a length of4; if the UE still processes the ports according to an orthogonal timeextension with a length of 2, great interference will be caused.Similarly, DMRS ports 8 and 11 can be processed based on an orthogonaltime extension with a length of 2, while DMRS ports 8 and 13 can only beprocessed according to an orthogonal time extension with a length of 4.

TABLE 1 Antenna port p [ w _(p)(0) w _(p)(1) w _(p)(2) w _(p)(3)] 7 [+1+1 +1 +1] 8 [+1 −1 +1 −1] 9 [+1 +1 +1 +1] 10 [+1 −1 +1 −1] 11 [+1 +1 −1−1] 12 [−1 −1 +1 +1] 13 [+1 −1 −1 +1] 14 [−1 +1 +1 −1]

In order that a DMRS port with respect to an E-PDCCH is processed basedon an orthogonal time extension with a length of 2, and also that, whena PDSCH with a rank of 5, 6 or 7 is scheduled by the E-PDCCH, a DMRSport with respect to a PDSCH is processed based on an orthogonal timeextension with a length of 4, the present invention proposes thefollowing limitation on the DMRS ports of the PDSCH; that is to say,when a DMRS port occupied by the E-PDCCH of the UE is v, a DMRS portp(v) is defined not to be used to demodulate the PDSCH, or another DMRSport is needed to replace the p(v), so that a reference signal port ofthe E-PDCCH and a reference signal port of the PDSCH are processed basedon orthogonal time extensions with different lengths, and that theE-PDCCH and the PDSCH can be multiplexed normally. Particularly, p(v) isdefined as follows:

${p(v)} = \left\{ {\begin{matrix}{11,{v = 7}} \\{13,{v = 8}} \\{12,{v = 9}} \\{14,{v = 10}}\end{matrix}.} \right.$

When the rank of the PDSCH is equal to 8, it may be considered not tosupport multiplexing of the reference signals of the E-PDCCH and thePDSCH. When the rank of the PDSCH is less than or equal to 4, theE-PDCCH and the PDSCH both use DMRS ports 7, 8, 9 and 10; as the fourDMRS ports are all based on an orthogonal time extension with a lengthof 2, a problem that a DMRS port is not available as a result of anotherDMRS port does not exist.

1010: A base station performs CRC check code addition, scrambling,encoding and rate matching on downlink control information of a UE, soas to obtain modulation symbols of a PDCCH. 1010 of FIG. 10 is similarto 810 of FIG. 8, and is not described here any further.

1020: The base station performs physical resource mapping on an E-PDCCHand a PDSCH, and allocates reference signal ports of the E-PDCCH and thePDSCH, where the E-PDCCH and the PDSCH are frequency-divisionmultiplexed in a same PRB pair or in different PRB pairs of a same RBG.According to the embodiment of the present invention, two methods forallocating reference signal ports of an E-PDCCH and a PDSCH areprovided.

A first method is to adjust, according to a DMRS port occupied by theE-PDCCH, a DMRS port of the PDSCH defined in LTE release 10. A principleof the method is to maximally multiplex PDSCH DMRS ports already definedin release 10; in other words, only a port that affects a DMRS portoccupied by the E-PDCCH is not used; for example, when the E-PDCCH usesDMRS port 7, the PDSCH will not use DMRS port 11.

When the rank is less than or equal to 4, for transmission of a PDSCH,the definition of PDSCH DMRS ports in release 10 can be completelyreused. Specifically, if a DMRS port used by an E-PDCCH is included inDMRS ports of a currently scheduled PDSCH, the DMRS port may also beconfigured to demodulate the E-PDCCH and the PDSCH; if the DMRS portused by the E-PDCCH is not included in the DMRS ports of the currentlyscheduled PDSCH, the DMRS port is only configured to demodulate theE-PDCCH. Optionally, if the definition of the PDSCH DMRS port in release10 is followed, for the currently allocated PDSCH, the DMRS port used bythe E-PDCCH is not included in the DMRS port of the currently scheduledPDSCH, but on a time-frequency resource where the DMRS port used by theE-PDCCH is located, another DMRS port based on CDM multiplexing isoccupied by a reference signal of the PDSCH; here, the DMRS port used bythe E-PDCCH may be used to replace another DMRS port on a sametime-frequency resource to demodulate the PDSCH.

When the rank is 5, 6 or 7, and a DMRS port that the base station usesto send the E-PDCCH to the UE is v, according to the definition of thePDSCH DMRS port in release 10, if a DMRS port needed by the currentlyscheduled PDSCH is p(v), the p(v) is replaced with another DMRS port.Three preferred methods are described as follows, but the presentinvention is not limited to the three methods. When the rank is 5 or 6,the p(v) is replaced with another DMRS port using a same RE set as thep(v), that is, DMRS port p(v)+2; when the rank is 7, the p(v) isreplaced with DMRS port 14. Optionally, when the rank is 5, 6 or 7, thep(v) is uniformly replaced with DMRS port 14. Optionally, when the rankR is 5, 6 or 7, the p(v) is uniformly replaced with DMRS port 7+R.

A second method is to use, according to the DMRS port v occupied by theE-PDCCH and the rank R of the currently scheduled PDSCH, R continuousDMRS ports starting from port v as PDSCH reference signal ports.

When the rank is less than or equal to 4, DMRS port 7+(v−7+r)mod 4 (r=0,. . . , R−1), may be used as a PDSCH reference signal port; that is tosay, port 7+(v−7+r)mod 4 replaces PDSCH DMRS port 7+r defined in release10. This method ensures that all E-PDCCH DMRS ports can be multiplexedfor PDSCH demodulation. Optionally, when the rank is 2, in order toavoid extra resource overhead which results from that two DMRS ports arerespectively mapped to two RE sets bearing a reference signal, animproved method may be used that, when the rank is 3 or 4, the foregoingmethod is still used; in other words, DMRS port 7+(v−7+r)mod 4 (r=0, . .. , R−1) may be used as the PDSCH reference signal port; however, whenthe rank is 2, two PDSCH DMRS ports are limited to be mapped to a sameRE set; that is to say, DMRS ports v and v+(−1)^((v-7)mod 2) are used totransmit the PDSCH.

When the rank R is 5, 6 and 7, if the DMRS port that the base stationuses to send the E-PDCCH to the UE is v, R continuous ports startingfrom DMRS port v are used; that is to say, DMRS port 7+(v−7+r)mod 8(r=0, . . . , R−1) are used as PDSCH reference signal ports; and if theR DMRS ports include p(v), p(v) is replaced with another DMRS port. Twopreferred methods are described as follows, but the present invention isnot limited to the two methods. For example, when the rank is 5, 6 or 7,p(v) is uniformly replaced with DMRS port 7+v mod 8. Optionally, whenthe rank R is 5, 6 and 7, p(v) is uniformly replaced with DMRS port7+(v−7+R)mod 8.

1030: The base station sends the mapped PDCCH and PDSCH to the UE.

The base station sends the reference signal of the E-PDCCH by using afirst reference signal port v. The base station sends a reference signalof the PDSCH by using at least one second reference signal port, anddetermines, according to the foregoing reference signal port allocationmethod, not to use a second reference signal port p(v) but to selectanother reference signal port to send the reference signal of the PDSCH,so that a reference signal port of the E-PDCCH and a reference signalport of the PDSCH are processed based on orthogonal time extensions withdifferent lengths, where the first reference signal port is one of theat least one second reference signal port.

1040: The UE demodulates the E-PDCCH based on a channel estimationresult.

The UE receives the reference signal of the E-PDCCH which is sent by thebase station by using the first reference signal port v and thereference signal of the PDSCH which is sent by the base station by usingat least one second reference signal port, where the PDSCH is invoked bythe E-PDCCH. The UE performs channel estimation by using the referencesignal of the E-PDCCH, so as to demodulate the E-PDCCH, and performschannel estimation by using the reference signal of the PDSCH, so as todemodulate the PDSCH. The UE determines, according to the foregoingreference signal port allocation method, not to use the reference signalof the PDSCH sent by the second reference signal port p(v) but to selectanother reference signal port to perform channel estimation, so that areference signal port of the E-PDCCH and a reference signal port of thePDSCH are processed based on orthogonal time extensions with differentlengths, where the first reference signal port is one of the at leastone second reference signal port.

Similarly, the foregoing method for allocating reference signal ports ofthe E-PDCCH and the PDSCH may be configured in the UE; a specific methodis similar to the method for allocating reference signal ports of theE-PDCCH and the PDSCH at a base station end, and is not described hereany further.

1050: If detecting its own E-PDCCH, the UE demodulates a correspondingPDSCH according to the downlink control information in the E-PDCCH, andfeeds back in the uplink according to whether the PDSCH demodulation iscorrect. 1050 in FIG. 10 is similar to 850 in FIG. 8, and is notdescribed here any further.

The method for transmitting downlink control information according tothe embodiment of the present invention is described above; withreference to FIG. 11 to FIG. 16, the following respectively describes abase station, a UE, and a system, as well as a corresponding storablemedium and a corresponding computer program product, according toembodiments of the present invention.

Embodiment 10

FIG. 11 is a schematic structural diagram of a base station 1100according to Embodiment 10 of the present invention. The base station1100 includes a mapping unit 1110 and a sending unit 1120. Theembodiment in FIG. 11 elaborates one or more steps of the method in theembodiment in FIG. 2.

The mapping unit 1110 maps, according to an order of OFDM symbols usedby an E-PDCCH of a UE, the E-PDCCH sequentially to REs used to transmitthe E-PDCCH in each OFDM symbol. The sending unit 1120 sends the E-PDCCHto the UE by using the REs, where the E-PDCCH and a PDSCH invoked by theE-PDCCH are frequency-division multiplexed.

In the embodiment of the present invention, the E-PDCCH can be mapped,according to the order of OFDM symbols used by the E-PDCCH of the UE,sequentially to the REs used to transmit the E-PDCCH in each OFDMsymbol, so that different eCCEs will not include a same E-PDCCHmodulation symbol, thereby avoiding that the UE judges a start positionof the E-PDCCH incorrectly. In addition, a problem that E-PDCCHs at asame start position but different aggregation levels are mixed up isalso solved.

According to the embodiment of the present invention, the mapping unit1110 maps, according to an order of L eCCEs allocated to the E-PDCCH ineach OFDM symbol, the E-PDCCH sequentially to REs occupied by the LeCCEs in the OFDM symbol, where L is an integer.

Optionally, as another embodiment, the mapping unit 1110 maps, accordingto an order of subcarriers in each OFDM symbol, the E-PDCCH sequentiallyto REs occupied by L eCCEs allocated to the E-PDCCH.

For operations executed by means of hardware of the base station 1100 orcooperation of hardware and corresponding software of the base station1100, reference may be made to the corresponding method in Embodiment 1,for example, 210 and 220 of the method in the foregoing Embodiment 1.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 210 and 220of the method the foregoing Embodiment 1.

In addition, a computer program product is further provided, includingthe foregoing computer readable medium.

Embodiment 11

FIG. 12 is a schematic structural diagram of a UE 1200 according toEmbodiment 11 of the present invention. The UE 1200 includes a receivingunit 1210 and an extracting unit 1220. The embodiment in FIG. 12elaborates one or more steps of the method in the embodiment in FIG. 3.

The receiving unit 1210 receives a downlink subframe from a basestation. The extracting unit 1220 extracts, in a blind detection processaccording to an order of OFDM symbols used by a candidate E-PDCCH in thedownlink subframe, modulation symbols of the candidate E-PDCCHsequentially from REs used to transmit the candidate E-PDCCH in eachOFDM symbol, and performs decoding and CRC check on the candidateE-PDCCH, where the E-PDCCH of the UE and a PDSCH invoked by the E-PDCCHof the UE are frequency-division multiplexed.

In the embodiment of the present invention, the E-PDCCH can be mapped,according to the order of OFDM symbols used by the E-PDCCH of the UE,sequentially to the REs used to transmit the E-PDCCH in each OFDMsymbol, so that different eCCEs will not include a same E-PDCCHmodulation symbol, thereby avoiding that the UE judges a start positionof the E-PDCCH incorrectly. In addition, a problem that E-PDCCHs at asame start position but different aggregation levels are mixed up isalso solved.

According to the embodiment of the present invention, the extractingunit 1220 sequentially extracts, according to an order of L eCCEsallocated to the candidate E-PDCCH in each OFDM symbol, modulationsymbols of the candidate E-PDCCH from REs occupied by the L eCCEs in theOFDM symbol, where L is an integer.

Optionally, as another embodiment, the extracting unit 1220 sequentiallyextracts, according to an order of subcarriers in each OFDM symbol, theE-PDCCH from REs occupied by L eCCEs allocated to the E-PDCCH.

For operations executed by means of hardware of the UE 1200 orcooperation of hardware and corresponding software of the UE 1200,reference may be made to the corresponding method in Embodiment 2, forexample, 310 and 320 of the method in the foregoing Embodiment 2.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 310 and 320of the method in the foregoing Embodiment 2.

Further, a computer program product is further provided, including theforegoing computer readable medium.

Embodiment 12

FIG. 13 is a schematic structural diagram of a base station 1300according to Embodiment 12 of the present invention. The base station1300 includes a determining unit 1310 and a sending unit 1320. Theembodiment in FIG. 13 elaborates one or more steps of the method in theembodiment in FIG. 4.

The determining unit 1310 is configured to determine a reference signalport according to an aggregation level of an E-PDCCH of a UE, whereE-PDCCHs at different aggregation levels correspond to differentreference signal ports, and the aggregation level indicates the quantityof eCCEs included in the E-PDCCH. The sending unit 1320 is configured tosend the E-PDCCH to the UE in a subframe, and send a reference signal ofthe E-PDCCH to the UE by using the determined reference signal port,where the E-PDCCH and a PDSCH invoked by the E-PDCCH arefrequency-division multiplexed.

According to the embodiment of the present invention, reference signalsof E-PDCCHs at different eCCE aggregation levels can be sent by usingdifferent DMRS ports, so that the UE can demodulate, according to adedicated DMRS reference signal of an E-PDCCH at each aggregation level,the E-PDCCH correctly, thereby avoiding a problem that the UE judges astart position of the E-PDCCH incorrectly. In addition, a problem thatE-PDCCHs at a same start position but different aggregation levels aremixed up is also solved.

According to the embodiment of the present invention, E-PDCCHs at a samestart position but different aggregation levels in the subframecorrespond to different reference signal ports.

Further, the determining unit 1310 may be specifically configured toselect, according to the aggregation level of the physical downlinkcontrol channel E-PDCCH of the UE, one or more reference signal portsfrom a reference signal port set corresponding to the aggregation levelas a reference signal port corresponding to the aggregation level, wherereference signal ports selected for E-PDCCHs at different aggregationlevels are different.

Further, the at a same start position in the subframe may include: at asame start position in a same physical resource block pair or differentphysical resource block pairs.

Further, E-PDCCHs, corresponding to different user equipments UEs, at asame aggregation level, and occupying a same physical resource,correspond to different reference signal ports.

For operations executed by means of hardware of the base station 1300 orcooperation of hardware and corresponding software of the base station1300, reference may be made to the corresponding method in Embodiment 3,for example, 410 and 420 of the method in the foregoing Embodiment 3.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 410 and 420of the method in the foregoing Embodiment 3.

In addition, a computer program product is further provided, includingthe foregoing computer readable medium.

Embodiment 13

FIG. 14 is a schematic structural diagram of a UE 1400 according toEmbodiment 13 of the present invention. The UE 1400 includes a receivingunit 1410 and a demodulating unit 1420. The embodiment in FIG. 14elaborates one or more steps of the method in the embodiment in FIG. 5.

The receiving unit 1410 receives, from a reference signal port in asubframe, a reference signal of a candidate E-PDCCH sent by a basestation, where candidate E-PDCCHs at different aggregation levelscorrespond to different reference signal ports, and the aggregationlevel indicates the quantity of eCCEs included in the candidate E-PDCCH.The demodulating unit 1420 performs channel estimation according to thereference signal, so as to demodulate the E-PDCCH, where the candidateE-PDCCH and a PDSCH invoked by the candidate E-PDCCH arefrequency-division multiplexed.

According to the embodiment of the present invention, reference signalsof E-PDCCHs at different eCCE aggregation levels can be sent by usingdifferent DMRS ports, so that the UE can demodulate, according to adedicated DMRS reference signal of an E-PDCCH at each aggregation level,the E-PDCCH correctly, thereby avoiding a problem that the UE judges astart position of the E-PDCCH incorrectly. In addition, a problem thatE-PDCCHs at a same start position but different aggregation levels aremixed up is also solved.

According to the embodiment of the present invention, candidate E-PDCCHsat a same start position but different aggregation levels in thesubframe correspond to different reference signal ports.

For operations executed by means of hardware of the UE 1400 orcooperation of hardware and corresponding software of the UE 1400,reference may be made to the corresponding method in Embodiment 4, forexample, 510 and 520 of the method in the foregoing Embodiment 4.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 510 and 520of the method in the foregoing Embodiment 4.

In addition, a computer program product is further provided, includingthe foregoing computer readable medium.

Embodiment 14

FIG. 15 is a schematic structural diagram of a base station 1500according to Embodiment 14 of the present invention. The base station1500 includes a sending unit 1510 and a determining unit 1520. Theembodiment in FIG. 15 elaborates one or more steps of the method in theembodiment in FIG. 6.

The sending unit 1510 sends a reference signal of the E-PDCCH by using afirst reference signal port v, and send a reference signal of the PDSCHby using at least one second reference signal port. The determining unit1520 determines not to use a second reference signal port p(v) to sendthe reference signal of the PDSCH, so that a reference signal port ofthe E-PDCCH and a reference signal port of the PDSCH are processed basedon orthogonal time extensions with different lengths, where the E-PDCCHand the PDSCH are frequency-division multiplexed, the first referencesignal port is one of the at least one second reference signal port, andv and p(v) are serial numbers of the reference signal ports.

According to the embodiment of the present invention, when using areference signal port to send a reference signal of a PDSCH results thata reference signal port of an E-PDCCH and the reference signal port ofthe PDSCH cannot be processed based on orthogonal time extensions withdifferent lengths, the reference signal port may be not used to send thereference signal of the PDSCH, so that the reference signal of the PDSCHand a reference signal of the E-PDCCH are multiplexed normally.

According to the embodiment of the present invention, the at least onesecond reference signal port includes at least one of PDSCH referencesignal ports 7, 8, 9, 10, 11, 12, 13 and 14 defined in LTE release 10,the first reference signal port includes an E-PDCCH reference signalport 7, 8, 9, or 10 defined in LTE release 10, and

${p(v)} = \left\{ {\begin{matrix}{11,{v = 7}} \\{13,{v = 8}} \\{12,{v = 9}} \\{14,{v = 10}}\end{matrix}.} \right.$

According to the embodiment of the present invention, when a rank R ofthe PDSCH is less than or equal to 4, the sending unit 1510 sends thereference signal of the PDSCH by using a PDSCH reference signal portdefined in LTE release 10; or when the rank R of the PDSCH is one of 5,6 and 7, the sending unit 1510 sends the reference signal of the PDSCHby using a PDSCH reference signal port defined in LTE release 1, andwhen needing to send the reference signal of the PDSCH by using thesecond reference signal port p(v) to, the sending unit 1510 replaces thereference signal port p(v) with another available reference signal portamong the PDSCH reference signal ports, where R is an integer.

Optionally, as another embodiment, when a rank R of the PDSCH is lessthan or equal to 4, the sending unit 1510 may send the reference signalof the PDSCH by using R reference signal ports 7+(v−7+r)mod 4 startingfrom the reference signal port v, where r=0, . . . , R−1, and R is aninteger; or, when the rank R of the PDSCH is equal to one of 5, 6 and 7,the sending unit 1510 may send the reference signal of the PDSCH byusing R reference signal ports 7+(v−7+r) mod 8 starting from thereference signal port v, and when the R reference signal ports includethe reference signal port p(v), replace the reference signal port p(v)with another reference signal port among the PDSCH reference signalports, where r=0, . . . , R−1.

For operations executed by means of hardware of the base station 1500 orcooperation of hardware and corresponding software of the base station1500, reference may be made to the corresponding method in Embodiment 5,for example, 610 and 620 of the method in the foregoing Embodiment 5.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 610 and 620of the method in the foregoing Embodiment 5.

In addition, a computer program product is further provided, includingthe foregoing computer readable medium.

Embodiment 15

FIG. 16 is a schematic structural diagram of a UE 1600 according toEmbodiment 15 of the present invention. The UE 1600 includes a receivingunit 1610, a demodulating unit 1620, and a determining unit 1630. Theembodiment in FIG. 16 elaborates one or more steps of the method in theembodiment in FIG. 7.

The receiving unit 1610 is configured to receive a reference signal ofan E-PDCCH which is sent by a base station by using a first referencesignal port v and a reference signal of a PDSCH which is sent by thebase station by using at least one second reference signal port, wherethe PDSCH is invoked by the E-PDCCH. The demodulating unit 1620 isconfigured to perform channel estimation by using the reference signalof the E-PDCCH, so as to demodulate the E-PDCCH, and perform channelestimation by using the reference signal of the PDSCH, so as todemodulate the PDSCH. The determining unit 1630 is configured todetermine not to use the reference signal of the PDSCH sent by thesecond reference signal port p(v) to perform channel estimation, so thata reference signal port of the E-PDCCH and a reference signal port ofthe PDSCH are processed based on orthogonal time extensions withdifferent lengths, where the E-PDCCH and the PDSCH arefrequency-division multiplexed, the first reference signal port is oneof the at least one second reference signal port, and v and p(v) areserial numbers of the reference signal ports.

According to the embodiment of the present invention, the at least onesecond reference signal port includes at least one of PDSCH referencesignal ports 7, 8, 9, 10, 11, 12, 13 and 14 defined in LTE release 10,the first reference signal port includes an E-PDCCH reference signalport 7, 8, 9, or 10 defined in LTE release 10, and

${p(v)} = \left\{ {\begin{matrix}{11,{v = 7}} \\{13,{v = 8}} \\{12,{v = 9}} \\{14,{v = 10}}\end{matrix}.} \right.$

According to the embodiment of the present invention, when a rank R ofthe PDSCH is less than or equal to 4, the demodulating unit 1620performs channel estimation by using a reference signal of the PDSCHsent by a PDSCH reference signal port defined in LTE release 10; or whenthe rank R of the PDSCH is one of 5, 6 and 7, the demodulating unit 1620performs channel estimation by using a reference signal of the PDSCHsent by a PDSCH reference signal port defined in LTE release 10, andwhen the UE needs to perform channel estimation by using the referencesignal of the PDSCH sent by the second reference signal port p(v),replaces the reference signal port p(v) with another available referencesignal port among the PDSCH reference signal ports to perform channelestimation, where R is an integer.

Optionally, as another embodiment, when a rank R of the PDSCH is lessthan or equal to 4, the demodulating unit 1620 may perform channelestimation by using reference signals of the PDSCH sent by R referencesignal ports 7+(v−7+r) mod 4 starting from the reference signal port v,where r=0, . . . , R−1, and R is an integer; or, when the rank R of thePDSCH is equal to one of 5, 6 and 7, the demodulating unit 1620 may toperform channel estimation by using reference signals of the PDSCH sentby R reference signal ports 7+(v−7+r)mod 8 starting from the referencesignal port v, and when the R reference signal ports include thereference signal port p(v), replace the reference signal port p(v) withanother reference signal port among the PDSCH reference signal ports toperform channel estimation, where r=0, . . . , R−1.

For operations executed by means of hardware of the UE 1600 orcooperation of hardware and corresponding software of the UE 1600,reference may be made to the corresponding method in Embodiment 6, forexample, 710, 720 and 730 of the method in the foregoing Embodiment 6.However, to avoid repetition, the steps are not described here anyfurther.

In addition, a computer readable media (or medium) is further provided,including a computer readable instruction that performs the followingoperation when executed, that is, an operation of executing 710 and 720of the method in the foregoing Embodiment 6.

In addition, a computer program product is further provided, includingthe foregoing computer readable medium.

A person of ordinary skill in the art may recognize that units andalgorithmic steps of examples described with reference to theembodiments disclosed herein may be implemented by means of electronichardware or combination of computer software and electronic hardware.Whether the functions are executed by hardware or software depends onparticular applications and design constraint conditions of thetechnical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present invention.

A person skilled in the art can clearly understand that, for convenienceand conciseness of description, for specific working processes of thedescribed systems, apparatuses and units, reference may be made tocorresponding processes in the foregoing method embodiments, which willnot be described here any further.

In the several embodiments provided in the present application, itshould be understood that the disclosed system, apparatus, and methodmay be implemented in other manners. For example, the describedapparatus embodiment is merely exemplary. For example, the unit divisionis merely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented through some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separated parts may be or may not be physicallyseparate, and the parts displayed as units may or may not be physicalunits, may be located in one position, or may be distributed on aplurality of network units. A part of or all of the units may beselected according to actual needs to achieve the objectives of thesolutions of the embodiments.

In addition, the functional units of each embodiment in the presentinvention may be integrated in a physical unit, or each of the units mayexist alone physically, or two or more units may be integrated into oneunit.

When the functions are implemented in a form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer-readable storage medium. Based on such anunderstanding, the technical solutions of the present inventionessentially, or the part contributing to the prior art, or a part of thetechnical solutions may be implemented in a form of a software product.The computer software product is stored in a storage medium and includesseveral instructions for instructing a computer device (which may be apersonal computer, a server, a network device, or the like) to performall or a part of the steps of the methods described in the embodimentsof the present invention. The foregoing storage medium includes: anymediums that can store program code, such as a USB flash drive, aremovable hard disk, a read-only memory (ROM), a random access memory(RAM), a magnetic disk, or an optical disc.

Embodiment 16

In LTE R-11, the quantity of aggregation levels corresponding to a UE isM; if E-PDCCHs at N aggregation levels among the M aggregation levelsare mixed up, correct reception of an E-PDCCH or a PDSCH by the UE willbe affected, where M is not less than N, and M and N are integers.

Downlink control channels E-PDCCHs have M aggregation levels, where eachaggregation level of N aggregation levels thereof corresponds to areference signal port set. With respect to a UE, for each aggregationlevel of the N aggregation levels, a base station selects a referencesignal port from a reference signal port set corresponding to theaggregation level as a reference signal port corresponding to theaggregation level; reference signal ports selected for the N aggregationlevels of the UE are different from each other; and the reference signalport set at least includes one reference signal port.

The base station sends the E-PDCCH to the UE in a subframe, and sends areference signal of the E-PDCCH to the UE by using a determinedreference signal port,

where N is less than or equal to M.

For E-PDCCH transmission, each physical resource block pair may include2 or 4 physical eCCEs, where each physical eCCE bears eCCEs of oneePDCCH, as shown in FIG. 17. An E-PDCCH at aggregation level L includesL logical eCCEs; the L logical eCCEs are mapped to L physical eCCEs; andcontrol information of the E-PDCCH is transmitted on the L physicaleCCEs.

If each PRB pair includes 4 eCCEs, according to a size of controlsignaling, the numbers of PRB pairs occupied by an ePDCCH correspondingto aggregation levels 2, 4, 8, 12, 16 and above 16 are respectively 1,1, 2, 3, 4 and above 4. For example, when a UE detects an E-PDCCH ataggregation level 8, if the first 4 eCCEs are detected successfully, theUE regards the aggregation level of the E-PDCCH as 4 and the quantity ofPRB pairs occupied as 1. In fact, the quantity of PRB pairs occupied bythe E-PDCCH is 2. In this case, the UE may possibly regard the rest 4eCCEs as resources to transmit a PDSCH, and receive the PDSCH on therest 4 eCCEs, which may cause incorrect reception of the PDSCH.Similarly, if each PRB pair includes two eCCEs, according to a size ofcontrol signaling, the numbers of PRB pairs occupied by an ePDCCHcorresponding to aggregation levels 2, 4, 8, 12, 16 and above 16 arerespectively 1, 2, 4, 6, 8 and above 8. When the E-PDCCH is received,the foregoing problem that aggregation levels are mixed up will alsooccur. Aggregation levels that are possible to be mixed up for a UE arepossibly N of the aggregation levels 2, 4, 8, 12, 16 and above 16, andeach aggregation level of the N aggregation levels corresponds to areference signal port set. A reference signal port corresponding toaggregation level L among the N aggregation levels of the UE is one ormore reference signal ports selected from a reference signal port setcorresponding to the aggregation level L. Reference signal portsselected for the N aggregation levels of the UE are different from eachother.

To be specific, for example:

If each physical resource block includes four physical eCCEs, areference signal port set corresponding to aggregation level 2 may beset 1, a reference signal port set corresponding to aggregation level 4may be set 2, and a reference signal port set corresponding toaggregation level 8 may be set 3. Reference signal ports included ineach set may be completely different, partially the same or thecompletely same. The quantity of reference signal ports respectivelyincluded in set 1, set 2 and set 3 is at least 1. For any UE, areference signal port selected from set 1 is r, a reference signal portselected from set 2 is s, and a reference signal port selected from set3 is t. A reference signal port corresponding to aggregation level 2 ofthe UE is r, a reference signal port corresponding to aggregation level4 of the UE is s, and a reference signal port corresponding toaggregation level 8 of the UE is t, where r, s and t are different fromeach other. For example, set 1 is {reference signal port 7, referencesignal port 8, reference signal port 9, reference signal port 10}, set 2is {reference signal port 8, reference signal port 9}, and set 3 is{reference signal port 7, reference signal port 10}. As shown in FIG.18, for UE1 (or all UEs in cell 1, aggregation level 2 corresponds toreference signal port 7 or 9, aggregation level 4 corresponds toreference signal port 8, and aggregation level 8 corresponds toreference signal port 10; for UE2 (or all UEs in cell 2, aggregationlevel 2 corresponds to reference signal port 8 or 10, aggregation level4 corresponds to reference signal port 9, and aggregation level 8corresponds to reference signal port 7. It can be seen that, ifreference signal ports are configured in such a manner, for a same UE,aggregation levels 2, 4 and 8 correspond to different reference signalports, which can avoid the problem that the aggregation levels are mixedup. Further, E-PDCCHs, corresponding to different user equipments UEs,at a same aggregation level, and occupying a same physical resource,correspond to different reference signal ports, and can supportmulti-user transmission. For example, for aggregation level 2, physicalresources that the first E-PDCCHs of UE1 and UE2 occupy are eCCE0 andeCCE1, while physical resources that the second E-PDCCHs of UE1 and UE2occupy are eCCE2 and eCCE3. For aggregation level 2, the first E-PDCCHsof UE1 and UE2 correspond to different reference signal ports, so as tosupport simultaneous transmission of UE1 and UE2 on eCCE0 and eCCE1; andthe second E-PDCCHs of UE1 and UE2 correspond to different referencesignal ports, so as to support simultaneous transmission of UE1 and UE2on eCCE2 and eCCE3.

If each physical resource block includes two physical eCCEs, a referencesignal port set corresponding to aggregation level 2 is set 1, areference signal port set corresponding to aggregation level 4 is set 2,and a reference signal port set corresponding to aggregation level 8 isset 3. Reference signal ports included in each set may be completelydifferent, partially the same or completely the same. The quantity ofreference signal ports respectively included in set 1, set 2 and set 3is at least 1. For any UE, a reference signal port selected from set 1is r, a reference signal port selected from set 2 is s, and a referencesignal port selected from set 3 is t. A reference signal portcorresponding to aggregation level 2 of the UE is r, a reference signalport corresponding to aggregation level 4 of the UE is s, and areference signal port corresponding to aggregation level 8 of the UE ist, where r, s and t are different from each other. For example, set 1 is{reference signal port 7, reference signal port 10}, set 2 is {referencesignal port 8, reference signal port 9}, and set 3 is {reference signalport 7, reference signal port 10}. As shown in FIG. 19, for UE1 (or allUEs in cell 1, aggregation level 2 corresponds to reference signal port7, aggregation level 4 corresponds to reference signal port 9, andaggregation level 8 corresponds to a reference signal port 10; for UE2(or all UEs in cell 2, aggregation level 2 corresponds to referencesignal port 10, aggregation level 4 corresponds to reference signal port8, and aggregation level 8 corresponds to reference signal port 7. Itcan be seen that, if reference signal ports are configured in such amanner, for a same UE, aggregation levels 2, 4 and 8 correspond todifferent reference signal ports, which can avoid the problem that theaggregation levels are mixed up. Further, E-PDCCHs, corresponding todifferent user equipments UEs, at a same aggregation level, andoccupying a same physical resource, correspond to different referencesignal ports, and can support multi-user transmission.

Further, that reference signal ports selected for the N aggregationlevels of the UE are different from each other may specifically be:reference signal ports selected for E-PDCCHs at the N aggregation levelsof the UE, which are mapped to a same physical resource start positionare different from each other, which may also be understood that,E-PDCCHs at a same start position but different aggregation levels inthe subframe correspond to different reference signal ports.

Further, the at a same start position in the subframe may include: at asame start position in a same physical resource block pair or differentphysical resource block pairs. The “at a same start position in thesubframe” herein may all be understood as above, and is not describedany further.

As shown in FIG. 20, for UE1 and UE2, in a same PRB pair, two E-PDCCHsare at aggregation level 2, where a first E-PDCCH is mapped to eCCE0 andeCCE1, where eCCE0 is a start position; and a second E-PDCCH is mappedto eCCE2 and eCCE3, where eCCE2 is a start position. One E-PDCCH is ataggregation level 4, which is mapped to eCCE0, eCCE1, eCCE2 and eCCE3,where eCCE0 is a start position. One E-PDCCH is at aggregation level 8,which is mapped to eCCE0, eCCE1, eCCE2 and eCCE3, as well as eCCE0,eCCE1, eCCE2 and eCCE3 of another PRB pair, where eCCE0 is a startposition.

Then, for UE1, reference signal ports selected for the two E-PDCCHs ataggregation level 2 are reference signal ports 7 and 10 respectively, areference signal port selected for the E-PDCCH at aggregation level 4 isreference signal port 8, and a reference signal port selected for theE-PDCCH at aggregation level 8 is reference signal port 10. It can beseen that reference signal ports selected for E-PDCCHs at aggregationlevels 2, 4 and 8 and mapped to a same physical resource start position(that is eCCE0 in this embodiment) are respectively reference signalports 7, 8 and 10, which are different from each other. For UE2,reference signal ports selected for the two E-PDCCHs at aggregationlevel 2 are reference signal ports 8 and 9 respectively, a referencesignal port selected for the E-PDCCH at aggregation level 4 is referencesignal port 9, and a reference signal port selected for the E-PDCCH ataggregation level 8 is reference signal port 7. It can be seen thatreference signal ports selected for E-PDCCHs at aggregation levels 2, 4and 8 and mapped to a same physical resource start position (that iseCCE0 in this embodiment) are respectively reference signal ports 8, 9and 7, which are different from each other. The at a same physicalresource start position may be understood as at a same start position inthe subframe. Further, the at a same start position in the subframeincludes: at a same start position in a same physical resource blockpair or different physical resource block pairs. That is to say, the ata same start position in the subframe may be at a same start position indifferent PRB pairs or at a same start position in identical PRB pairs.As shown in FIG. 21, physical resource position 1 is eCCE0 of PRB pair1, physical resource position 2 is eCCE0 of PRB pair 2, and physicalresource position 3 is eCCE0 of PRB pair 3. A same start position indifferent PRB pairs means that positions of the PRB pairs are different,but start positions in the PRB pairs are the same; for example, if onestart position is physical resource position 1, and another startposition is physical resource position 3, and it may be called at a samestart position in different PRB pairs. A same start position inidentical PRB pairs means that positions of PRB pairs are the same andstart positions in the PRB pairs are also the same; for example, if thetwo start positions both are physical resource position 1 or the twostart positions both are physical resource position 3, it may be calledat a same start position in identical PRB pairs.

The methods of configuring a reference signal port set and selecting areference signal port from the reference signal port set are shared bythe base station and the UE, and may be defined and configured by thesystem previously, or notified to the UE by the base station, orobtained according to a parameter of the UE, or the like.

Understandably, the selected reference signal ports are only used fordescription; a person skilled in the art may deduce another referencesignal port set or an example of selecting a reference signal port fromthe set, which is not limited in the present invention.

It should be noted that, due to limited space, mutual reference may bemade to corresponding embodiments of the present invention, and samecontent will not be described repetitively.

The foregoing descriptions are merely specific embodiments of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any variation or replacement readily figured outby a person skilled in the art within the technical scope disclosed inthe present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention shall be subject to the protection scope of the claims.

1-68. (canceled)
 69. A method for transmitting a downlink controlsignal, comprising: mapping, by a base station, an enhanced physicaldownlink control channel (E-PDCCH) of a user equipment (UE) sequentiallyto resource elements for transmitting the E-PDCCH in each orthogonalfrequency division multiplexing (OFDM) symbol according to an order ofthe OFDM symbols used by the E-PDCCH of the UE; and sending, by the basestation, the E-PDCCH to the UE by using the mapped resource elements;wherein the E-PDCCH and a physical downlink shared channel (PDSCH)invoked by the E-PDCCH are frequency-division multiplexed.
 70. Themethod according to claim 69, wherein mapping the E-PDCCH sequentiallyto the resource elements comprises: mapping the E-PDCCH sequentially toresource elements occupied by L control channel elements in each OFDMsymbol according to an order of the L control channel elements allocatedto the E-PDCCH in the OFDM symbol, wherein L is an integer.
 71. Themethod according to claim 70, wherein mapping the E-PDCCH sequentiallyto the resource elements occupied by the L control channel elements ineach OFDM symbol comprises: mapping modulation symbols of the E-PDCCHwith index numbers of$j_{0} + {\sum\limits_{q = 0}^{l - 1}\; N_{q}} + \left\lbrack {0,\ldots \mspace{14mu},{N_{l} - 1}} \right\rbrack$sequentially to a set R_(l) of resource elements, wherein the set R_(l)is a set of resource elements occupied by the l^(th) control channelelement among the L control channel elements comprised in the E-PDCCH inthe OFDM symbol; j₀ is a start position of the modulation symbols of theE-PDCCH mapped in the OFDM symbol; N_(l) is the quantity of the resourceelements in the set R_(l); and N_(l), j₀, l and q are integers.
 72. Themethod according to claim 69, wherein mapping the E-PDCCH sequentiallyto the resource elements comprises: mapping the E-PDCCH sequentially toresource elements occupied by L control channel elements allocated tothe E-PDCCH according to an order of subcarriers in each OFDM symbol,wherein L is an integer.
 73. The method according to claim 72, whereinmapping the E-PDCCH sequentially to the resource elements occupied by Lcontrol channel elements allocated to the E-PDCCH comprises: mappingmodulation symbols of the E-PDCCH with index numbers of j₀+[0, . . . ,N−1] sequentially to a set R of resource elements, wherein j₀ is a startposition of the modulation symbols of the E-PDCCH mapped in the OFDMsymbol; the set R is a set of resource elements occupied by the Lcontrol channel elements comprised in the E-PDCCH in the OFDM symbol; Nis the quantity of the resource elements in the set R; and N and j₀ areintegers.
 74. A method for receiving a downlink control signal,comprising: receiving, by a user equipment (UE), a downlink subframefrom a base station; extracting, by the UE, modulation symbols of acandidate enhanced physical downlink control channel (E-PDCCH)sequentially from resource elements mapped to the candidate E-PDCCH ineach orthogonal frequency division multiplexing (OFDM) symbol accordingto an order of the OFDM symbols used by the candidate E-PDCCH in thedownlink subframe; and performing a decoding and a cyclic redundancycheck (CRC) on the candidate E-PDCCH; wherein the E-PDCCH of the UE anda physical downlink shared channel (PDSCH) invoked by the E-PDCCH of theUE are frequency-division multiplexed.
 75. The method according to claim74, wherein extracting the modulation symbols of the candidate E-PDCCHcomprises: extracting the modulation symbols of the candidate E-PDCCHsequentially from resource elements occupied by L control channelelements in each OFDM symbol according to an order of the L controlchannel elements allocated to the E-PDCCH in the OFDM symbol, wherein Lis an integer.
 76. The method according to claim 75, wherein extractingthe modulation symbols of the candidate E-PDCCH sequentially fromresource elements occupied by the L control channel elements in eachOFDM symbol comprises: extracting modulation symbols of the candidateE-PDCCH and with index numbers of$j_{0} + {\sum\limits_{q = 0}^{l - 1}\; N_{q}} + \left\lbrack {0,\ldots \mspace{14mu},{N_{l} - 1}} \right\rbrack$from a set R_(l) of resource elements, wherein the set R_(l) is a set ofresource elements occupied by the l^(th) control channel element amongthe L control channel elements comprised in the modulation symbols ofthe candidate E-PDCCH in the OFDM symbol; j₀ is a start position of themodulation symbols of the candidate E-PDCCH mapped in the OFDM symbol;N_(l) is the quantity of the resource elements in the set R_(l); andN_(l), j₀, l and q are integers.
 77. The method according to claim 74,wherein extracting the modulation symbols of the candidate E-PDCCHcomprises: extracting, by the UE, the modulation symbols of thecandidate E-PDCCH from resource elements occupied by L control channelelements allocated to the candidate E-PDCCH according to an order ofsubcarriers in each OFDM symbol.
 78. The method according to claim 77,wherein extracting the modulation symbols of the candidate E-PDCCH fromresource elements occupied by L control channel elements allocated tothe candidate E-PDCCH comprises: extracting modulation symbols of thecandidate E-PDCCH and with index numbers of j₀+[0, . . . , N−1] from aset R of resource elements, wherein j₀ is a start position of themodulation symbols of the candidate E-PDCCH mapped in the OFDM symbol;the set R is a set of resource elements occupied by the L controlchannel elements comprised in the modulation symbols of the candidateE-PDCCH in the OFDM symbol; N is the quantity of the resource elementsin the set R; and N and j₀ are integers.
 79. A base station, comprising:a mapping processor, configured to map an enhanced physical downlinkcontrol channel (E-PDCCH) of a user equipment (UE) sequentially toresource elements for transmitting the E-PDCCH in each orthogonalfrequency division multiplexing (OFDM) symbol according to an order ofthe OFDM symbols used by the E-PDCCH of the UE; and a transmitter,configured to send the E-PDCCH to the UE by using the mapped resourceelements; wherein the E-PDCCH and a physical downlink shared channel(PDSCH) invoked by the E-PDCCH are frequency-division multiplexed. 80.The base station according to claim 79, wherein the mapping processormaps the E-PDCCH sequentially to resource elements occupied by L controlchannel elements in each OFDM symbol according to an order of the Lcontrol channel elements allocated to the E-PDCCH in the OFDM symbol,wherein L is an integer.
 81. The base station according to claim 79,wherein the mapping processor maps the E-PDCCH sequentially to resourceelements occupied by L control channel elements allocated to the E-PDCCHaccording to an order of subcarriers in each OFDM symbol.
 82. A userequipment, comprising: a receiver, configured to receive a downlinksubframe from a base station; and an extracting processor, configured tosequentially extract modulation symbols of a candidate enhanced physicaldownlink control channel (E-PDCCH) sequentially from resource elementsmapped to the candidate E-PDCCH in each orthogonal frequency divisionmultiplexing (OFDM) symbol according to an order of the OFDM symbolsused by the candidate E-PDCCH in the downlink subframe, and perform adecoding and a cyclic redundancy check (CRC) on the candidate E-PDCCH;wherein an E-PDCCH of the user equipment and a physical downlink sharedchannel (PDSCH) invoked by the E-PDCCH of the user equipment arefrequency-division multiplexed.
 83. The user equipment according toclaim 82, wherein the extracting processor extracts the candidateE-PDCCH sequentially from resource elements occupied by L controlchannel elements in each OFDM symbol according to an order of the Lcontrol channel elements allocated to the candidate E-PDCCH in the OFDMsymbol, wherein L is an integer.
 84. The user equipment according toclaim 82, wherein the extracting processor extracts the modulationsymbols of the candidate E-PDCCH from resource elements occupied by Lcontrol channel elements allocated to the candidate E-PDCCH according toan order of subcarriers in each OFDM symbol.